Built-in MCP endpoint (Streamable HTTP) on top of the public API (#105)

AI clients talk to the instance directly at /api/mcp — under the /api/
path (deviation from the issue's literal /mcp) so every existing reverse
proxy already routes it; no deployment changes anywhere.

- Transport: official @modelcontextprotocol/sdk server, STATELESS — each
  POST builds a fresh server+transport pair, no session store, replicas
  stay trivial; GET/DELETE answer 405. Auth per PAT bearer (#104 tokens),
  per-token rate limit (429 + Retry-After).
- Own switches, independent of REST: instance mcp.enabled (admin
  settings, default off; off = 404, feature invisible) + pond setting
  mcpEnabled (pond-settings toggle, default off) — pinned independent in
  both directions by tests.
- Tools (thin wrappers over the #104 services, same permission gates,
  audit-logged writes): list_ponds, list_pages, read_page, search,
  create_page, update_page (replace semantics through the collab-owned
  restore path — open editors converge), add_comment, list_labels,
  set_page_labels (exact replace), export_pond (link to the REST ZIP).
  Tool errors carry the api error codes; results carry stable slugs/ids.
  MCP resources stay the documented stage-2 stretch goal.
- Deliberately on the SDK's low-level Server API with a hand-written tool
  table (mcp-tools.ts): the typed registerTool generics drove tsc out of
  memory in a program this size; manual Zod validation keeps the wire
  behavior explicit.
- PublicApiService exposure filtering parameterized ('api' | 'mcp',
  shared pondFeatureEnabled helper) — one implementation, two switches.
- Docs: "Connect Claude Code / MCP clients" section in public-api.md
  (claude mcp add one-liner + mcp-remote bridge for stdio clients).

Verification: 8-test e2e pack driving the real MCP SDK client over
Streamable HTTP against a listening api (initialize + tools/list, switch
independence in both directions, anonymous/garbage 401, opt-in 404
semantics, page roundtrip incl. restore-NOTIFY, labels/comments, read
scope blocked from writes with scope_required); live check through the
web proxy against the seeded stack (tools list, create, read, update,
search — LIVE CHECK PASSED); full api suite 61/61 files green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwZ4jR4KFAPvpjWevfUGX1

apps/api/package.json

@@ -18,6 +18,7 @@
   "dependencies": {
     "@dorfteich/plugin-sdk": "workspace:*",
     "@dorfteich/shared": "workspace:*",
+    "@modelcontextprotocol/sdk": "^1.29.0",
     "@nestjs/common": "^11.0.0",
     "@nestjs/core": "^11.0.0",
     "@nestjs/platform-express": "^11.0.0",

apps/api/src/app.module.ts

@@ -19,6 +19,7 @@ import { LabelsModule } from './labels/labels.module';
 import { LegalModule } from './legal/legal.module';
 import { LinksModule } from './links/links.module';
 import { MailModule } from './mail/mail.module';
+import { McpModule } from './mcp/mcp.module';
 import { MembersModule } from './members/members.module';
 import { PagesModule } from './pages/pages.module';
 import { PermissionsModule } from './permissions/permissions.module';
@@ -71,6 +72,7 @@ import { VersionsModule } from './versions/versions.module';
     MembersModule,
     PublicModule,
     PublicApiModule,
+    McpModule,
     ImportExportModule,
     PluginsModule,
     AuthModule,

apps/api/src/main.ts

@@ -76,7 +76,7 @@ async function bootstrap(): Promise<void> {
   // The public API (issue #104) lives at /api/public/v1 — its controllers
   // declare the full path and are excluded from the SPA prefix.
   app.setGlobalPrefix('api/v1', {
-    exclude: ['api/public/v1', 'api/public/v1/{*path}'],
+    exclude: ['api/public/v1', 'api/public/v1/{*path}', 'api/mcp'],
   });
   app.enableShutdownHooks();
 

apps/api/src/mcp/mcp-tools.ts

@@ -0,0 +1,172 @@
+import { z } from 'zod';
+
+/**
+ * The MCP tool table (issue #105): names, English descriptions, and input
+ * schemas — the JSON Schema served on tools/list is written by hand next
+ * to the Zod schema that actually validates calls. Kept as plain data (and
+ * validated in mcp.service.ts, not through the SDK's typed helpers): the
+ * SDK's generic tool registration blows up TypeScript's inference when
+ * combined with a program this size.
+ */
+
+const pond = z.string().min(1);
+const page = z.string().min(1);
+
+export const MCP_TOOL_INPUTS = {
+  list_ponds: z.object({}),
+  list_pages: z.object({ pond }),
+  read_page: z.object({ pond, page }),
+  search: z.object({
+    query: z.string().min(1),
+    pond: pond.optional(),
+    label: z.string().min(1).optional(),
+  }),
+  create_page: z.object({
+    pond,
+    title: z.string().min(1).max(200),
+    markdown: z.string().default(''),
+  }),
+  update_page: z
+    .object({
+      pond,
+      page,
+      title: z.string().min(1).max(200).optional(),
+      markdown: z.string().optional(),
+    })
+    .refine((input) => input.title !== undefined || input.markdown !== undefined, {
+      message: 'title or markdown required',
+    }),
+  add_comment: z.object({ pond, page, text: z.string().min(1) }),
+  list_labels: z.object({ pond }),
+  set_page_labels: z.object({ pond, page, labelIds: z.array(z.string()) }),
+  export_pond: z.object({ pond }),
+} as const;
+
+export type McpToolName = keyof typeof MCP_TOOL_INPUTS;
+
+const pondProp = { type: 'string', description: 'Pond slug (from list_ponds)' } as const;
+const pageProp = { type: 'string', description: 'Page slug (from list_pages or search)' } as const;
+
+/** What tools/list advertises; must stay in sync with the Zod table above. */
+export const MCP_TOOL_DEFINITIONS: {
+  name: McpToolName;
+  description: string;
+  inputSchema: object;
+}[] = [
+  {
+    name: 'list_ponds',
+    description:
+      'List the ponds (workspaces) this token can reach through MCP. ' +
+      'Returns slugs — every other tool takes a pond slug.',
+    inputSchema: { type: 'object', properties: {} },
+  },
+  {
+    name: 'list_pages',
+    description: 'List the readable pages of a pond: slug, title, labels, timestamps.',
+    inputSchema: { type: 'object', properties: { pond: pondProp }, required: ['pond'] },
+  },
+  {
+    name: 'read_page',
+    description: 'Read one page as Markdown plus metadata (title, labels, timestamps).',
+    inputSchema: {
+      type: 'object',
+      properties: { pond: pondProp, page: pageProp },
+      required: ['pond', 'page'],
+    },
+  },
+  {
+    name: 'search',
+    description:
+      'Full-text search across the reachable ponds. Returns pond/page slugs and snippets ' +
+      'with matches wrapped in **…** — chain into read_page.',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        query: { type: 'string', description: 'Search terms' },
+        pond: { ...pondProp, description: 'Restrict to one pond (slug)' },
+        label: { type: 'string', description: 'Restrict to pages carrying this label id' },
+      },
+      required: ['query'],
+    },
+  },
+  {
+    name: 'create_page',
+    description:
+      'Create a page from a title and Markdown content (requires a write-scope token and ' +
+      'editor rights in the pond). Returns the created page including its slug.',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        pond: pondProp,
+        title: { type: 'string', maxLength: 200 },
+        markdown: { type: 'string', description: 'Initial content as Markdown' },
+      },
+      required: ['pond', 'title'],
+    },
+  },
+  {
+    name: 'update_page',
+    description:
+      'Update a page: set a new title and/or REPLACE the whole content with the given ' +
+      'Markdown (write scope required). The change is applied through the live ' +
+      'collaborative document, so open editors converge; the previous state stays in the ' +
+      'version history.',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        pond: pondProp,
+        page: pageProp,
+        title: { type: 'string', maxLength: 200 },
+        markdown: { type: 'string', description: 'Replacement content as Markdown' },
+      },
+      required: ['pond', 'page'],
+    },
+  },
+  {
+    name: 'add_comment',
+    description:
+      "Comment on a page (write scope; the pond's comment policy applies). Markdown is " +
+      'supported.',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        pond: pondProp,
+        page: pageProp,
+        text: { type: 'string', description: 'Comment body (Markdown)' },
+      },
+      required: ['pond', 'page', 'text'],
+    },
+  },
+  {
+    name: 'list_labels',
+    description: "The pond's label tree (ids + names) — ids feed set_page_labels.",
+    inputSchema: { type: 'object', properties: { pond: pondProp }, required: ['pond'] },
+  },
+  {
+    name: 'set_page_labels',
+    description:
+      "Replace a page's labels with exactly the given label ids (write scope). An empty " +
+      'list removes all labels.',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        pond: pondProp,
+        page: pageProp,
+        labelIds: {
+          type: 'array',
+          items: { type: 'string' },
+          description: 'Label ids from list_labels',
+        },
+      },
+      required: ['pond', 'page', 'labelIds'],
+    },
+  },
+  {
+    name: 'export_pond',
+    description:
+      'A download link for the whole pond as a Markdown ZIP. The link goes through the ' +
+      'public REST API, so the instance REST switch and the same token are needed to ' +
+      'fetch it.',
+    inputSchema: { type: 'object', properties: { pond: pondProp }, required: ['pond'] },
+  },
+];

apps/api/src/mcp/mcp.controller.ts

@@ -0,0 +1,97 @@
+import {
+  Controller,
+  Delete,
+  Get,
+  HttpException,
+  HttpStatus,
+  NotFoundException,
+  Post,
+  Req,
+  Res,
+  UnauthorizedException,
+} from '@nestjs/common';
+import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
+import type { Request, Response } from 'express';
+
+import { Public } from '../auth/auth.guard';
+import { RateLimitService } from '../rate-limit/rate-limit.service';
+import { ApiTokensService } from '../public-api/api-tokens.service';
+import { InstanceSettingsService } from '../settings/instance-settings.service';
+import { McpService } from './mcp.service';
+
+/** Same budget as the REST surface — one shared runaway stop per token. */
+const RATE_LIMIT = { limit: 120, windowSeconds: 60 };
+
+/**
+ * The MCP Streamable-HTTP endpoint (issue #105) at `/api/mcp` — under the
+ * `/api/` path on purpose: every existing reverse proxy (stages,
+ * self-hosters, the bundled Caddyfile) already routes it to the api, so no
+ * deployment changes anywhere. Stateless: each POST builds a fresh server +
+ * transport pair (no session store), which keeps api replicas trivial;
+ * GET/DELETE (SSE resumption, session teardown) answer 405 accordingly.
+ *
+ * Gating mirrors the REST guard with the MCP switches: instance
+ * `mcp.enabled` off → 404 (feature invisible), then PAT bearer auth and the
+ * per-token rate limit. Pond opt-in (`mcpEnabled`) is enforced inside every
+ * tool (McpService).
+ */
+@Controller('api/mcp')
+@Public()
+export class McpController {
+  constructor(
+    private readonly mcp: McpService,
+    private readonly tokens: ApiTokensService,
+    private readonly settings: InstanceSettingsService,
+    private readonly rateLimits: RateLimitService,
+  ) {}
+
+  @Post()
+  async handle(@Req() request: Request, @Res() response: Response): Promise<void> {
+    if (!(await this.settings.get('mcp.enabled'))) throw new NotFoundException();
+
+    const header = request.headers.authorization ?? '';
+    const raw = header.startsWith('Bearer ') ? header.slice('Bearer '.length).trim() : '';
+    const validated = raw ? await this.tokens.validate(raw) : null;
+    if (!validated) throw new UnauthorizedException();
+
+    const limited = await this.rateLimits.hit(
+      'mcp',
+      `token:${validated.token.id}`,
+      RATE_LIMIT.limit,
+      RATE_LIMIT.windowSeconds,
+    );
+    if (!limited.allowed) {
+      response.setHeader('Retry-After', String(limited.retryAfterSeconds));
+      throw new HttpException({ code: 'rate_limited' }, HttpStatus.TOO_MANY_REQUESTS);
+    }
+
+    const server = this.mcp.buildServer(validated.user, validated.token);
+    const transport = new StreamableHTTPServerTransport({
+      // Stateless mode: no session ids, every request stands alone.
+      sessionIdGenerator: undefined,
+    });
+    response.on('close', () => {
+      void transport.close();
+      void server.close();
+    });
+    await server.connect(transport);
+    // The body was parsed by the global express.json middleware.
+    await transport.handleRequest(request, response, request.body);
+  }
+
+  @Get()
+  async methodNotAllowed(@Res() response: Response): Promise<void> {
+    if (!(await this.settings.get('mcp.enabled'))) throw new NotFoundException();
+    // Stateless server: no SSE stream to resume, no session to delete.
+    response.status(HttpStatus.METHOD_NOT_ALLOWED).json({
+      jsonrpc: '2.0',
+      error: { code: -32000, message: 'Method not allowed — stateless transport, POST only' },
+      id: null,
+    });
+  }
+
+  @Delete()
+  async deleteNotAllowed(@Res() response: Response): Promise<void> {
+    await this.methodNotAllowed(response);
+  }
+}

apps/api/src/mcp/mcp.e2e.db.test.ts

@@ -0,0 +1,335 @@
+import { INestApplication } from '@nestjs/common';
+import { Client as McpClient } from '@modelcontextprotocol/sdk/client/index.js';
+import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';
+import { PAGE_RESTORE_CHANNEL, type ApiTokenCreatedView } from '@dorfteich/shared';
+import { PrismaClient } from '@prisma/client';
+import { Client as PgClient } from 'pg';
+import request from 'supertest';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+
+import { InstanceSettingsService } from '../settings/instance-settings.service';
+import { createTestApp, sessionCookieOf } from '../testing/test-app';
+import { createTestPrisma, hasTestDb, uniqueSuffix } from '../testing/test-db';
+import { UsersService } from '../users/users.service';
+
+/**
+ * The built-in MCP endpoint end to end (issue #105), driven by the real
+ * MCP SDK client over Streamable HTTP against a listening api: initialize
+ * + tools/list, the page roundtrip (create → read → update via the
+ * collab-safe path → search), the independent instance/pond switches (404
+ * semantics), scope enforcement, and label management.
+ */
+describe.skipIf(!hasTestDb)('mcp endpoint (e2e, issue #105)', () => {
+  let app: INestApplication;
+  let prisma: PrismaClient;
+  let baseUrl: string;
+  const suffix = uniqueSuffix();
+  const password = 'mcp ist angebunden 1';
+  const ids: Record<string, string> = {};
+  const cookies: Record<string, string> = {};
+  let pondId: string;
+  let pondSlug: string;
+  let writeToken: string;
+  let readToken: string;
+
+  const restoreNotifies: { pageId: string }[] = [];
+  let listenClient: PgClient;
+
+  const api = () => request(app.getHttpServer());
+
+  async function connect(token: string): Promise<McpClient> {
+    const client = new McpClient({ name: 'dorfteich-e2e', version: '0.0.0' });
+    const transport = new StreamableHTTPClientTransport(new URL(`${baseUrl}/api/mcp`), {
+      requestInit: { headers: { Authorization: `Bearer ${token}` } },
+    });
+    await client.connect(transport);
+    return client;
+  }
+
+  function textOf(result: unknown): string {
+    const content = (result as { content: { type: string; text?: string }[] }).content;
+    return content.map((c) => c.text ?? '').join('\n');
+  }
+
+  async function makeUser(handle: string): Promise<void> {
+    const users = app.get(UsersService);
+    const username = `mcp-${handle}-${suffix}`;
+    const user = await users.createUser({
+      username,
+      email: `${username}@example.org`,
+      displayName: `Mcp ${handle}`,
+      password,
+      locale: 'en',
+    });
+    await users.markEmailVerified(user.id);
+    ids[handle] = user.id;
+    cookies[handle] = sessionCookieOf(
+      await api()
+        .post('/api/v1/auth/login')
+        .send({ usernameOrEmail: username, password })
+        .expect(200),
+    );
+  }
+
+  beforeAll(async () => {
+    prisma = createTestPrisma();
+    await prisma.rateLimit.deleteMany({});
+    app = await createTestApp();
+    // The MCP client needs a real HTTP server, not supertest's ephemeral one.
+    await app.listen(0);
+    baseUrl = await app.getUrl();
+    baseUrl = baseUrl.replace('[::1]', '127.0.0.1').replace(/\/$/, '');
+
+    await makeUser('owner');
+    await makeUser('siteadmin');
+    await prisma.user.update({ where: { id: ids.siteadmin! }, data: { isSiteAdmin: true } });
+    await api()
+      .put(`/api/v1/admin/quotas/user/${ids.owner!}/additional_ponds`)
+      .set('Cookie', cookies.siteadmin!)
+      .send({ value: 100 })
+      .expect(200);
+
+    const pond = await api()
+      .post('/api/v1/ponds')
+      .set('Cookie', cookies.owner!)
+      .send({ name: `MCP Pond ${suffix}` })
+      .expect(201);
+    pondId = pond.body.id;
+    pondSlug = pond.body.slug;
+
+    const mint = async (scope: 'read' | 'write'): Promise<string> => {
+      const res = await api()
+        .post('/api/v1/users/me/api-tokens')
+        .set('Cookie', cookies.owner!)
+        .send({ name: `mcp-${scope}-${suffix}`, scope })
+        .expect(201);
+      return (res.body as ApiTokenCreatedView).token;
+    };
+    writeToken = await mint('write');
+    readToken = await mint('read');
+
+    listenClient = new PgClient({ connectionString: process.env.TEST_DATABASE_URL });
+    await listenClient.connect();
+    listenClient.on('notification', (message) => {
+      if (message.channel === PAGE_RESTORE_CHANNEL && message.payload) {
+        restoreNotifies.push(JSON.parse(message.payload) as { pageId: string });
+      }
+    });
+    await listenClient.query(`LISTEN ${PAGE_RESTORE_CHANNEL}`);
+  });
+
+  afterAll(async () => {
+    await listenClient.end().catch(() => undefined);
+    const all = Object.values(ids);
+    await prisma.instanceSetting.deleteMany({ where: { key: { in: ['mcp.enabled'] } } });
+    await prisma.quotaOverride.deleteMany({ where: { subjectId: { in: all } } });
+    await prisma.auditEntry.deleteMany({ where: { actorId: { in: all } } });
+    await prisma.apiToken.deleteMany({ where: { userId: { in: all } } });
+    const ponds = await prisma.pond.findMany({
+      where: { ownerId: { in: all } },
+      select: { id: true },
+    });
+    const pondIds = ponds.map((p) => p.id);
+    await prisma.comment.deleteMany({ where: { page: { pondId: { in: pondIds } } } });
+    await prisma.pageVersion.deleteMany({ where: { page: { pondId: { in: pondIds } } } });
+    await prisma.page.deleteMany({ where: { pondId: { in: pondIds } } });
+    await prisma.label.deleteMany({ where: { pondId: { in: pondIds } } });
+    await prisma.roleGrant.deleteMany({ where: { pondId: { in: pondIds } } });
+    await prisma.pondUsage.deleteMany({ where: { pondId: { in: pondIds } } });
+    await prisma.pond.deleteMany({ where: { id: { in: pondIds } } });
+    await prisma.session.deleteMany({ where: { userId: { in: all } } });
+    await prisma.userIdentity.deleteMany({ where: { userId: { in: all } } });
+    await prisma.rateLimit.deleteMany({});
+    await prisma.user.deleteMany({ where: { id: { in: all } } });
+    await prisma.$disconnect();
+    await app.close();
+  });
+
+  it('is invisible while the instance switch is off, independent of the REST switch', async () => {
+    // The REST switch being ON must not open MCP.
+    await app.get(InstanceSettingsService).set('api.enabled', true, ids.owner!);
+    const res = await fetch(`${baseUrl}/api/mcp`, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Accept: 'application/json, text/event-stream',
+        Authorization: `Bearer ${writeToken}`,
+      },
+      body: JSON.stringify({ jsonrpc: '2.0', method: 'ping', id: 1 }),
+    });
+    expect(res.status).toBe(404);
+    await app.get(InstanceSettingsService).set('api.enabled', false, ids.owner!);
+    await app.get(InstanceSettingsService).set('mcp.enabled', true, ids.owner!);
+  });
+
+  it('rejects anonymous and garbage tokens', async () => {
+    for (const headers of [{}, { Authorization: 'Bearer dt_pat_garbage' }] as Record<
+      string,
+      string
+    >[]) {
+      const res = await fetch(`${baseUrl}/api/mcp`, {
+        method: 'POST',
+        headers: {
+          'Content-Type': 'application/json',
+          Accept: 'application/json, text/event-stream',
+          ...headers,
+        },
+        body: JSON.stringify({ jsonrpc: '2.0', method: 'ping', id: 1 }),
+      });
+      expect(res.status).toBe(401);
+    }
+  });
+
+  it('initializes and lists the tool set', async () => {
+    const client = await connect(writeToken);
+    const tools = await client.listTools();
+    const names = tools.tools.map((tool) => tool.name).sort();
+    expect(names).toEqual([
+      'add_comment',
+      'create_page',
+      'export_pond',
+      'list_labels',
+      'list_pages',
+      'list_ponds',
+      'read_page',
+      'search',
+      'set_page_labels',
+      'update_page',
+    ]);
+    await client.close();
+  });
+
+  it('hides ponds without the MCP opt-in, then exposes them', async () => {
+    const client = await connect(writeToken);
+    const empty = await client.callTool({ name: 'list_ponds', arguments: {} });
+    expect(JSON.parse(textOf(empty))).toEqual([]);
+    const denied = await client.callTool({
+      name: 'list_pages',
+      arguments: { pond: pondSlug },
+    });
+    expect(denied.isError).toBe(true);
+    expect(textOf(denied)).toContain('not_found');
+
+    await api()
+      .patch(`/api/v1/ponds/${pondId}`)
+      .set('Cookie', cookies.owner!)
+      .send({ mcpEnabled: true })
+      .expect(200);
+
+    const ponds = await client.callTool({ name: 'list_ponds', arguments: {} });
+    expect(JSON.parse(textOf(ponds)).map((p: { slug: string }) => p.slug)).toEqual([pondSlug]);
+    await client.close();
+  });
+
+  it('round-trips a page: create, read, update through the collab path, search', async () => {
+    const client = await connect(writeToken);
+
+    const created = await client.callTool({
+      name: 'create_page',
+      arguments: {
+        pond: pondSlug,
+        title: `MCP Page ${suffix}`,
+        markdown: `# Von MCP\n\nSeerose${suffix} im **Teich**.`,
+      },
+    });
+    expect(created.isError).toBeFalsy();
+    const page = JSON.parse(textOf(created)) as { slug: string; markdown: string };
+    expect(page.markdown).toContain(`Seerose${suffix}`);
+
+    const read = await client.callTool({
+      name: 'read_page',
+      arguments: { pond: pondSlug, page: page.slug },
+    });
+    expect(JSON.parse(textOf(read)).markdown).toContain('**Teich**');
+
+    restoreNotifies.length = 0;
+    const updated = await client.callTool({
+      name: 'update_page',
+      arguments: { pond: pondSlug, page: page.slug, markdown: 'Ersetzt durch MCP.' },
+    });
+    expect(updated.isError).toBeFalsy();
+    const pageRow = await prisma.page.findFirst({ where: { pondId, slug: page.slug } });
+    const versions = await prisma.pageVersion.findMany({
+      where: { pageId: pageRow!.id, trigger: 'MANUAL' },
+    });
+    expect(versions.some((v) => v.label === 'API update')).toBe(true);
+    await new Promise((resolve) => setTimeout(resolve, 200));
+    expect(restoreNotifies.some((n) => n.pageId === pageRow!.id)).toBe(true);
+
+    const found = await client.callTool({
+      name: 'search',
+      arguments: { query: `seerose${suffix}` },
+    });
+    const hits = JSON.parse(textOf(found)) as { pageSlug: string }[];
+    expect(hits.map((h) => h.pageSlug)).toContain(page.slug);
+
+    const link = await client.callTool({
+      name: 'export_pond',
+      arguments: { pond: pondSlug },
+    });
+    expect(JSON.parse(textOf(link)).url).toContain(`/api/public/v1/ponds/${pondSlug}/export`);
+
+    await client.close();
+  });
+
+  it('manages labels and comments through tools', async () => {
+    const client = await connect(writeToken);
+    const pageResult = await client.callTool({
+      name: 'create_page',
+      arguments: { pond: pondSlug, title: `Labelled ${suffix}`, markdown: 'x' },
+    });
+    const page = JSON.parse(textOf(pageResult)) as { slug: string };
+
+    // Labels are Pond-Admin work — the owner is one.
+    const label = await api()
+      .post(`/api/v1/ponds/${pondId}/labels`)
+      .set('Cookie', cookies.owner!)
+      .send({ name: `mcp-label-${suffix}` })
+      .expect(201);
+    const labelId = label.body.id as string;
+
+    const tree = await client.callTool({ name: 'list_labels', arguments: { pond: pondSlug } });
+    expect(textOf(tree)).toContain(`mcp-label-${suffix}`);
+
+    const set = await client.callTool({
+      name: 'set_page_labels',
+      arguments: { pond: pondSlug, page: page.slug, labelIds: [labelId] },
+    });
+    expect(JSON.parse(textOf(set)).map((l: { id: string }) => l.id)).toEqual([labelId]);
+    const cleared = await client.callTool({
+      name: 'set_page_labels',
+      arguments: { pond: pondSlug, page: page.slug, labelIds: [] },
+    });
+    expect(JSON.parse(textOf(cleared))).toEqual([]);
+
+    const comment = await client.callTool({
+      name: 'add_comment',
+      arguments: { pond: pondSlug, page: page.slug, text: 'Eine **Anmerkung** via MCP' },
+    });
+    expect(JSON.parse(textOf(comment)).html).toContain('<strong>Anmerkung</strong>');
+    await client.close();
+  });
+
+  it('lets read tokens list/read/search but blocks writes with scope_required', async () => {
+    const client = await connect(readToken);
+    const ponds = await client.callTool({ name: 'list_ponds', arguments: {} });
+    expect(JSON.parse(textOf(ponds)).length).toBe(1);
+    const pages = await client.callTool({ name: 'list_pages', arguments: { pond: pondSlug } });
+    expect(JSON.parse(textOf(pages)).length).toBeGreaterThan(0);
+
+    const denied = await client.callTool({
+      name: 'create_page',
+      arguments: { pond: pondSlug, title: 'nope' },
+    });
+    expect(denied.isError).toBe(true);
+    expect(textOf(denied)).toContain('scope_required');
+    await client.close();
+  });
+
+  it('keeps the REST surface closed while only MCP is on', async () => {
+    await request(app.getHttpServer())
+      .get('/api/public/v1/me')
+      .set('Authorization', `Bearer ${writeToken}`)
+      .expect(404);
+  });
+});

apps/api/src/mcp/mcp.module.ts

@@ -0,0 +1,20 @@
+import { Module } from '@nestjs/common';
+
+import { LabelsModule } from '../labels/labels.module';
+import { PermissionsModule } from '../permissions/permissions.module';
+import { PublicApiModule } from '../public-api/public-api.module';
+import { RateLimitModule } from '../rate-limit/rate-limit.module';
+import { SettingsModule } from '../settings/settings.module';
+import { McpController } from './mcp.controller';
+import { McpService } from './mcp.service';
+
+/**
+ * Built-in MCP endpoint (issue #105): tools are thin wrappers over the
+ * public-API services (#104), gated by their own instance + pond switches.
+ */
+@Module({
+  imports: [PublicApiModule, PermissionsModule, LabelsModule, SettingsModule, RateLimitModule],
+  controllers: [McpController],
+  providers: [McpService],
+})
+export class McpModule {}

apps/api/src/mcp/mcp.service.ts

@@ -0,0 +1,253 @@
+import { ForbiddenException, HttpException, Injectable, NotFoundException } from '@nestjs/common';
+import { Server } from '@modelcontextprotocol/sdk/server/index.js';
+import { CallToolRequestSchema, ListToolsRequestSchema } from '@modelcontextprotocol/sdk/types.js';
+import { pondFeatureEnabled, pondSettingsSchema } from '@dorfteich/shared';
+import { ApiToken, User } from '@prisma/client';
+import { z } from 'zod';
+
+import { AppConfig } from '../config/app-config.service';
+import { LabelsService } from '../labels/labels.service';
+import { PermissionService } from '../permissions/permission.service';
+import { PrismaService } from '../prisma/prisma.service';
+import { ApiTokensService } from '../public-api/api-tokens.service';
+import { PublicApiService } from '../public-api/public-api.service';
+import { MCP_TOOL_DEFINITIONS, MCP_TOOL_INPUTS, type McpToolName } from './mcp-tools';
+
+type ToolResult = { content: { type: 'text'; text: string }[]; isError?: boolean };
+
+/**
+ * The built-in MCP server (issue #105): thin tools over the public-API
+ * service (#104), authenticated per request with the same personal access
+ * tokens and gated by its own switches — instance `mcp.enabled` plus the
+ * per-pond `mcpEnabled` opt-in. One stateless server instance is built per
+ * request (the transport holds no session), so multiple api replicas stay
+ * trivial.
+ *
+ * Deliberately on the SDK's low-level Server API with the hand-written
+ * tool table (mcp-tools.ts): the typed `registerTool` helpers sent
+ * TypeScript's inference out of memory in a program this size, and manual
+ * Zod validation keeps the wire behavior explicit anyway.
+ *
+ * Permission model: a tool call acts AS the token's user. Pond/page checks
+ * mirror the REST guard exactly (opt-in + restriction → 404 semantics,
+ * write-on-readable → 403, scopes) — errors surface as MCP tool errors
+ * carrying the api error code.
+ */
+@Injectable()
+export class McpService {
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly permissions: PermissionService,
+    private readonly publicApi: PublicApiService,
+    private readonly labels: LabelsService,
+    private readonly tokens: ApiTokensService,
+    private readonly config: AppConfig,
+  ) {}
+
+  buildServer(user: User, token: ApiToken): Server {
+    const server = new Server(
+      { name: 'dorfteich', version: this.config.env.APP_VERSION },
+      { capabilities: { tools: {} } },
+    );
+
+    server.setRequestHandler(ListToolsRequestSchema, () => ({
+      tools: MCP_TOOL_DEFINITIONS,
+    }));
+
+    server.setRequestHandler(CallToolRequestSchema, async (request) => {
+      const name = request.params.name as McpToolName;
+      const schema = MCP_TOOL_INPUTS[name];
+      if (!schema) {
+        return toolError(`unknown tool: ${String(request.params.name)}`);
+      }
+      const parsed = schema.safeParse(request.params.arguments ?? {});
+      if (!parsed.success) {
+        return toolError(
+          `invalid arguments: ${parsed.error.issues.map((i) => `${i.path.join('.') || '(root)'} ${i.message}`).join('; ')}`,
+        );
+      }
+      try {
+        return await this.call(user, token, name, parsed.data as never);
+      } catch (error) {
+        const code =
+          error instanceof HttpException
+            ? ((error.getResponse() as { code?: string }).code ?? `http_${error.getStatus()}`)
+            : 'internal_error';
+        return toolError(code);
+      }
+    });
+
+    return server;
+
+    // Note: MCP resources (dorfteich://pond/page) are the documented
+    // stage-2 stretch goal — tools cover every current client flow.
+  }
+
+  private async call<Name extends McpToolName>(
+    user: User,
+    token: ApiToken,
+    name: Name,
+    args: z.infer<(typeof MCP_TOOL_INPUTS)[Name]>,
+  ): Promise<ToolResult> {
+    const input = args as Record<string, string> & { labelIds?: string[] };
+    switch (name) {
+      case 'list_ponds':
+        return asJson(await this.publicApi.listPonds(user, token, 'mcp'));
+
+      case 'list_pages':
+        await this.assertPondExposed(input.pond!, token);
+        return asJson(await this.publicApi.listPages(user, input.pond!));
+
+      case 'read_page':
+        await this.assertPondExposed(input.pond!, token);
+        await this.requirePage(user, input.pond!, input.page!, 'read');
+        return asJson(await this.publicApi.getPage(input.pond!, input.page!));
+
+      case 'search': {
+        if (input.pond) await this.assertPondExposed(input.pond, token);
+        return asJson(
+          await this.publicApi.searchPages(
+            user,
+            token,
+            { q: input.query!, pond: input.pond, label: input.label },
+            'mcp',
+          ),
+        );
+      }
+
+      case 'create_page':
+        this.requireWriteScope(token);
+        await this.assertPondExposed(input.pond!, token);
+        await this.requirePondRole(user, input.pond!, 'editor');
+        return asJson(
+          await this.publicApi.createPage(user, token, input.pond!, {
+            title: input.title!,
+            markdown: input.markdown ?? '',
+          }),
+        );
+
+      case 'update_page':
+        this.requireWriteScope(token);
+        await this.assertPondExposed(input.pond!, token);
+        await this.requirePage(user, input.pond!, input.page!, 'write');
+        return asJson(
+          await this.publicApi.updatePage(user, token, input.pond!, input.page!, {
+            title: input.title,
+            markdown: input.markdown,
+          }),
+        );
+
+      case 'add_comment':
+        this.requireWriteScope(token);
+        await this.assertPondExposed(input.pond!, token);
+        await this.requirePage(user, input.pond!, input.page!, 'read');
+        return asJson(
+          await this.publicApi.createComment(user, token, input.pond!, input.page!, {
+            body: input.text!,
+          }),
+        );
+
+      case 'list_labels':
+        await this.assertPondExposed(input.pond!, token);
+        await this.requirePondRole(user, input.pond!, 'reader');
+        return asJson(await this.publicApi.listLabels(user, input.pond!));
+
+      case 'set_page_labels': {
+        this.requireWriteScope(token);
+        await this.assertPondExposed(input.pond!, token);
+        const pageRow = await this.requirePage(user, input.pond!, input.page!, 'write');
+        const wantedIds = input.labelIds ?? [];
+        const current = await this.labels.pageLabels(user, pageRow.id);
+        const wanted = new Set(wantedIds);
+        for (const label of current) {
+          if (!wanted.has(label.id)) await this.labels.unassign(user, pageRow.id, label.id);
+        }
+        const have = new Set(current.map((label) => label.id));
+        for (const labelId of wantedIds) {
+          if (!have.has(labelId)) {
+            await this.publicApi.assignLabel(user, token, input.pond!, input.page!, labelId);
+          }
+        }
+        return asJson(await this.labels.pageLabels(user, pageRow.id));
+      }
+
+      case 'export_pond': {
+        await this.assertPondExposed(input.pond!, token);
+        await this.requirePondRole(user, input.pond!, 'reader');
+        const base = this.config.env.APP_BASE_URL.replace(/\/+$/, '');
+        return asJson({
+          url: `${base}/api/public/v1/ponds/${encodeURIComponent(input.pond!)}/export/markdown`,
+          hint: 'GET with the same Authorization: Bearer header; responds with a ZIP stream.',
+        });
+      }
+    }
+  }
+
+  private requireWriteScope(token: ApiToken): void {
+    if (this.tokens.scopeOf(token) !== 'write') {
+      throw new ForbiddenException({ code: 'scope_required' });
+    }
+  }
+
+  /** Mirror of the REST guard with the MCP flag: opted in via `mcpEnabled`
+   * and within the token's pond restriction, else 404 semantics. */
+  private async assertPondExposed(slug: string, token: ApiToken): Promise<void> {
+    const pond = await this.prisma.pond.findFirst({
+      where: { slug, deletedAt: null },
+      select: { id: true, settings: true },
+    });
+    if (!pond) throw new NotFoundException({ code: 'not_found' });
+    const settings = pondSettingsSchema.safeParse(pond.settings ?? {});
+    if (!settings.success || !pondFeatureEnabled(settings.data, 'mcp')) {
+      throw new NotFoundException({ code: 'not_found' });
+    }
+    if (token.pondIds.length > 0 && !token.pondIds.includes(pond.id)) {
+      throw new NotFoundException({ code: 'not_found' });
+    }
+  }
+
+  private async requirePondRole(
+    user: User,
+    slug: string,
+    role: 'reader' | 'editor',
+  ): Promise<void> {
+    const pond = await this.prisma.pond.findFirst({
+      where: { slug, deletedAt: null },
+      select: { id: true },
+    });
+    if (!pond) throw new NotFoundException({ code: 'not_found' });
+    if (await this.permissions.hasPondRole(user, pond.id, role)) return;
+    if (role !== 'reader' && (await this.permissions.canSeePond(user, pond.id))) {
+      throw new ForbiddenException({ code: 'forbidden' });
+    }
+    throw new NotFoundException({ code: 'not_found' });
+  }
+
+  private async requirePage(
+    user: User,
+    pondSlug: string,
+    pageSlug: string,
+    action: 'read' | 'write',
+  ): Promise<{ id: string; pondId: string }> {
+    const page = await this.prisma.page.findFirst({
+      where: { slug: pageSlug, deletedAt: null, pond: { slug: pondSlug, deletedAt: null } },
+      select: { id: true, pondId: true },
+    });
+    if (!page) throw new NotFoundException({ code: 'not_found' });
+    if (!(await this.permissions.canAccessPage(user, page, 'read'))) {
+      throw new NotFoundException({ code: 'not_found' });
+    }
+    if (action === 'write' && !(await this.permissions.canAccessPage(user, page, 'write'))) {
+      throw new ForbiddenException({ code: 'forbidden' });
+    }
+    return page;
+  }
+}
+
+function asJson(value: unknown): ToolResult {
+  return { content: [{ type: 'text', text: JSON.stringify(value, null, 2) }] };
+}
+
+function toolError(code: string): ToolResult {
+  return { isError: true, content: [{ type: 'text', text: `Error: ${code}` }] };
+}

apps/api/src/ponds/ponds.service.ts

@@ -152,7 +152,8 @@ export class PondsService {
       input.sidebarSort !== undefined ||
       input.fonts !== undefined ||
       input.commentPolicy !== undefined ||
-      input.apiEnabled !== undefined;
+      input.apiEnabled !== undefined ||
+      input.mcpEnabled !== undefined;
     const settings = !settingsChanged
       ? undefined
       : {
@@ -161,6 +162,7 @@ export class PondsService {
           ...(input.fonts !== undefined ? { fonts: input.fonts } : {}),
           ...(input.commentPolicy !== undefined ? { commentPolicy: input.commentPolicy } : {}),
           ...(input.apiEnabled !== undefined ? { apiEnabled: input.apiEnabled } : {}),
+          ...(input.mcpEnabled !== undefined ? { mcpEnabled: input.mcpEnabled } : {}),
         };
     const updated = await this.prisma.pond.update({
       where: { id },

apps/api/src/public-api/public-api.guard.ts

@@ -10,7 +10,7 @@ import {
   UnauthorizedException,
 } from '@nestjs/common';
 import { Reflector } from '@nestjs/core';
-import { pondSettingsSchema, type ApiTokenScope } from '@dorfteich/shared';
+import { pondFeatureEnabled, pondSettingsSchema, type ApiTokenScope } from '@dorfteich/shared';
 import type { ApiToken } from '@prisma/client';
 import type { Response } from 'express';
 
@@ -110,7 +110,9 @@ export class PublicApiGuard implements CanActivate {
     });
     if (!pond) throw new NotFoundException();
     const settings = pondSettingsSchema.safeParse(pond.settings ?? {});
-    if (!settings.success || !settings.data.apiEnabled) throw new NotFoundException();
+    if (!settings.success || !pondFeatureEnabled(settings.data, 'api')) {
+      throw new NotFoundException();
+    }
     if (token.pondIds.length > 0 && !token.pondIds.includes(pond.id)) {
       throw new NotFoundException();
     }

apps/api/src/public-api/public-api.service.ts

@@ -4,6 +4,7 @@ import {
   SEARCH_HIGHLIGHT_START,
   editorSchema,
   markdownToDoc,
+  pondFeatureEnabled,
   pondSettingsSchema,
   type CommentListFilter,
   type CreateCommentInput,
@@ -21,6 +22,7 @@ import {
   type PublicSearchResultView,
   type PublicUpdateLabelInput,
   type PublicUpdatePageInput,
+  type PondExposureFeature,
   type PondView,
 } from '@dorfteich/shared';
 import { Node } from 'prosemirror-model';
@@ -74,13 +76,14 @@ export class PublicApiService {
     };
   }
 
-  /** The API-enabled ponds visible to the token's user, within restriction. */
-  async listPonds(user: User, token: ApiToken): Promise<PublicPondView[]> {
-    const visible = await this.ponds.listVisible(user);
-    return visible
-      .filter((pond) => pond.settings.apiEnabled)
-      .filter((pond) => token.pondIds.length === 0 || token.pondIds.includes(pond.id))
-      .map((pond) => this.pondView(pond));
+  /** The exposed ponds visible to the token's user, within restriction. */
+  async listPonds(
+    user: User,
+    token: ApiToken,
+    feature: PondExposureFeature = 'api',
+  ): Promise<PublicPondView[]> {
+    const ponds = await this.listPondRowsExposed(user, token, feature);
+    return ponds.map((pond) => this.pondView(pond));
   }
 
   async getPond(slug: string): Promise<PublicPondView> {
@@ -176,8 +179,9 @@ export class PublicApiService {
     user: User,
     token: ApiToken,
     query: PublicSearchQuery,
+    feature: PondExposureFeature = 'api',
   ): Promise<PublicSearchResultView[]> {
-    const exposed = await this.exposedPondIds(user, token);
+    const exposed = await this.exposedPondIds(user, token, feature);
     let pondId: string | undefined;
     if (query.pond) {
       const pond = await this.requirePond(query.pond);
@@ -371,15 +375,23 @@ export class PublicApiService {
     return new Map(labels.map((label) => [label.id, label.name]));
   }
 
-  private async exposedPondIds(user: User, token: ApiToken): Promise<Set<string>> {
-    const ponds = await this.listPondRowsExposed(user, token);
+  private async exposedPondIds(
+    user: User,
+    token: ApiToken,
+    feature: PondExposureFeature,
+  ): Promise<Set<string>> {
+    const ponds = await this.listPondRowsExposed(user, token, feature);
     return new Set(ponds.map((pond) => pond.id));
   }
 
-  private async listPondRowsExposed(user: User, token: ApiToken): Promise<{ id: string }[]> {
+  private async listPondRowsExposed(
+    user: User,
+    token: ApiToken,
+    feature: PondExposureFeature,
+  ): Promise<PondView[]> {
     const visible = await this.ponds.listVisible(user);
     return visible
-      .filter((pond) => pond.settings.apiEnabled)
+      .filter((pond) => pondFeatureEnabled(pond.settings, feature))
       .filter((pond) => token.pondIds.length === 0 || token.pondIds.includes(pond.id));
   }
 

apps/api/src/settings/instance-settings.service.ts

@@ -53,6 +53,9 @@ export const INSTANCE_SETTINGS = {
   // /api/public/v1 route answers 404 while disabled. Individual ponds
   // additionally opt in through their pond settings (`apiEnabled`).
   'api.enabled': z.boolean().default(false),
+  // Built-in MCP endpoint master switch (issue #105, default off) —
+  // independent of the REST switch; ponds opt in via `mcpEnabled`.
+  'mcp.enabled': z.boolean().default(false),
   // Backup targets (ADR 0015, issue #103). The backup sidecar reads these
   // rows directly (apps/backup settings.ts — keep the schemas in sync); the
   // Nextcloud app password is NOT here, it lives in the secret store

apps/api/src/testing/test-app.ts

@@ -36,7 +36,7 @@ export async function createTestApp(
   app.useBodyParser('json', { limit: '8mb' });
   // Mirrors main.ts: the public API (issue #104) declares its full path.
   app.setGlobalPrefix('api/v1', {
-    exclude: ['api/public/v1', 'api/public/v1/{*path}'],
+    exclude: ['api/public/v1', 'api/public/v1/{*path}', 'api/mcp'],
   });
   await app.init();
   return app;

apps/web/src/api-tokens/ApiOptInSetting.tsx

@@ -14,21 +14,23 @@ export function ApiOptInSetting({
   pondId,
   pondSlug,
   value,
+  mcpValue,
 }: {
   pondId: string;
   pondSlug: string;
   value: boolean;
+  mcpValue: boolean;
 }): React.JSX.Element {
   const { t } = useTranslation('apiTokens');
   const queryClient = useQueryClient();
   const [error, setError] = useState<unknown>(null);
   const [saved, setSaved] = useState(false);
 
-  const save = async (enabled: boolean): Promise<void> => {
+  const save = async (patch: { apiEnabled?: boolean; mcpEnabled?: boolean }): Promise<void> => {
     setError(null);
     setSaved(false);
     try {
-      await apiPatch(`/ponds/${pondId}`, { apiEnabled: enabled });
+      await apiPatch(`/ponds/${pondId}`, patch);
       await queryClient.invalidateQueries({ queryKey: ['pond', pondSlug] });
       setSaved(true);
     } catch (err) {
@@ -44,11 +46,20 @@ export function ApiOptInSetting({
         <input
           type="checkbox"
           checked={value}
-          onChange={(event) => void save(event.target.checked)}
+          onChange={(event) => void save({ apiEnabled: event.target.checked })}
         />
         {t('pond.label')}
       </label>
       <p className="api-opt-in__hint">{t('pond.hint')}</p>
+      <label className="api-opt-in__label">
+        <input
+          type="checkbox"
+          checked={mcpValue}
+          onChange={(event) => void save({ mcpEnabled: event.target.checked })}
+        />
+        {t('pond.mcpLabel')}
+      </label>
+      <p className="api-opt-in__hint">{t('pond.mcpHint')}</p>
     </div>
   );
 }

apps/web/src/pages/AdminSettingsPage.tsx

@@ -21,6 +21,7 @@ interface InstanceSettings {
   'quota.storageBytes': number;
   'quota.maxFileBytes': number;
   'api.enabled': boolean;
+  'mcp.enabled': boolean;
   'upload.allowedExtensions': string[];
   'upload.svgPolicy': 'reject' | 'sanitize';
   'legal.imprint': string;
@@ -195,11 +196,11 @@ function PublicApiSettingsForm({ settings }: { settings: InstanceSettings }): Re
   const [error, setError] = useState<unknown>(null);
   const [saved, setSaved] = useState(false);
 
-  async function save(enabled: boolean): Promise<void> {
+  async function save(patch: Record<string, boolean>): Promise<void> {
     setError(null);
     setSaved(false);
     try {
-      await apiPatch('/admin/settings', { 'api.enabled': enabled });
+      await apiPatch('/admin/settings', patch);
       await queryClient.invalidateQueries({ queryKey: ['admin', 'settings'] });
       setSaved(true);
     } catch (err) {
@@ -216,11 +217,20 @@ function PublicApiSettingsForm({ settings }: { settings: InstanceSettings }): Re
         <input
           type="checkbox"
           checked={settings['api.enabled']}
-          onChange={(event) => void save(event.target.checked)}
+          onChange={(event) => void save({ 'api.enabled': event.target.checked })}
         />
         {t('admin.label')}
       </label>
       <p className="api-opt-in__hint">{t('admin.hint')}</p>
+      <label className="api-opt-in__label">
+        <input
+          type="checkbox"
+          checked={settings['mcp.enabled']}
+          onChange={(event) => void save({ 'mcp.enabled': event.target.checked })}
+        />
+        {t('admin.mcpLabel')}
+      </label>
+      <p className="api-opt-in__hint">{t('admin.mcpHint')}</p>
     </section>
   );
 }

apps/web/src/pages/PondSettingsPage.tsx

@@ -111,6 +111,7 @@ export function PondSettingsPage(): React.JSX.Element {
             pondId={pond.data.id}
             pondSlug={pondSlug}
             value={pond.data.settings.apiEnabled}
+            mcpValue={pond.data.settings.mcpEnabled}
           />
         </section>
       )}

docs/self-hosting/README.md

@@ -137,9 +137,10 @@ bundle from Nextcloud by hand.
 ## Public REST API
 
 Scripts and integrations can talk to the instance through a
-token-authenticated API at `/api/public/v1` — off by default, enabled per
-instance and per pond. Details, token walkthrough, and the OpenAPI
-document: [public-api.md](public-api.md).
+token-authenticated API at `/api/public/v1`, and MCP clients (Claude Code
+and friends) through the built-in MCP endpoint at `/api/mcp` — both off by
+default, enabled per instance and per pond. Details, token walkthrough,
+and the OpenAPI document: [public-api.md](public-api.md).
 
 ## Health & troubleshooting
 

docs/self-hosting/public-api.md

@@ -52,6 +52,46 @@ curl -H "Authorization: Bearer dt_pat_..." \
 Deliberately not in v1 (stage 2): attachment upload, version endpoints,
 webhooks.
 
+## Connect Claude Code / MCP clients
+
+The instance ships its own MCP endpoint (Streamable HTTP) at `/api/mcp` —
+no extra process. It has **its own switches**, independent of the REST
+API: the instance switch under _Admin → Settings → Public API_ ("Enable
+the built-in MCP endpoint") and a per-pond opt-in in the pond settings.
+Authentication uses the same personal access tokens.
+
+Claude Code (or any Streamable-HTTP client):
+
+```sh
+claude mcp add --transport http dorfteich https://your-instance.example/api/mcp \
+  --header "Authorization: Bearer dt_pat_..."
+```
+
+Stdio-only clients bridge with `mcp-remote`:
+
+```json
+{
+  "mcpServers": {
+    "dorfteich": {
+      "command": "npx",
+      "args": [
+        "mcp-remote",
+        "https://your-instance.example/api/mcp",
+        "--header",
+        "Authorization: Bearer dt_pat_..."
+      ]
+    }
+  }
+}
+```
+
+Tools: `list_ponds`, `list_pages`, `read_page`, `search`, `create_page`,
+`update_page` (replace semantics, collab-safe like the REST PATCH),
+`add_comment`, `list_labels`, `set_page_labels`, `export_pond`. A tool
+call acts as the token's user; write tools need the `write` scope, and
+ponds without the MCP opt-in stay invisible (404 semantics). The endpoint
+is stateless — no sessions to manage, safe behind load balancers.
+
 ## Security notes
 
 - Bearer tokens only — no cookies are involved, so there is no CSRF

packages/shared/i18n/de/apiTokens.json

@@ -39,13 +39,17 @@
     "title": "Öffentliche API",
     "label": "Diesen Teich über die öffentliche API freigeben",
     "hint": "Standardmäßig aus. Wenn aktiviert, erreichen Nutzer diesen Teich mit ihren API-Tokens — mit genau den Berechtigungen, die sie hier ohnehin haben. Der instanzweite API-Schalter muss ebenfalls an sein.",
-    "saved": "Gespeichert."
+    "saved": "Gespeichert.",
+    "mcpLabel": "Diesen Teich für KI-Assistenten freigeben (MCP)",
+    "mcpHint": "Standardmäßig aus und unabhängig vom REST-Schalter. Wenn aktiviert, erreichen MCP-Clients wie Claude Code diesen Teich mit einem API-Token — wieder mit genau den Berechtigungen des Nutzers. Der instanzweite MCP-Schalter muss ebenfalls an sein."
   },
   "admin": {
     "title": "Öffentliche API",
     "label": "Öffentliche REST-API aktivieren",
     "hint": "Hauptschalter (standardmäßig aus). Nutzer erstellen dann Personal-Access-Tokens in ihren Einstellungen; jeder Teich gibt sich zusätzlich über seine Teich-Einstellungen frei. Dokumentation: /api/public/v1/openapi.json",
     "save": "Speichern",
-    "saved": "Gespeichert."
+    "saved": "Gespeichert.",
+    "mcpLabel": "Eingebauten MCP-Endpoint aktivieren",
+    "mcpHint": "Hauptschalter (standardmäßig aus), unabhängig von der REST-API. MCP-Clients verbinden sich mit einem API-Token auf /api/mcp; jeder Teich gibt sich zusätzlich über seine Teich-Einstellungen frei. Siehe docs/self-hosting/public-api.md."
   }
 }

packages/shared/i18n/en/apiTokens.json

@@ -39,13 +39,17 @@
     "title": "Public API",
     "label": "Expose this pond through the public API",
     "hint": "Off by default. When enabled, users can reach this pond with their API tokens — with exactly the permissions they have here anyway. The instance-wide API switch must also be on.",
-    "saved": "Saved."
+    "saved": "Saved.",
+    "mcpLabel": "Expose this pond to AI assistants (MCP)",
+    "mcpHint": "Off by default and independent of the REST toggle. When enabled, MCP clients such as Claude Code can reach this pond with an API token — again with exactly the user's permissions. The instance-wide MCP switch must also be on."
   },
   "admin": {
     "title": "Public API",
     "label": "Enable the public REST API",
     "hint": "Master switch (default off). Users then create personal access tokens in their settings; each pond additionally opts in via its pond settings. Documentation: /api/public/v1/openapi.json",
     "save": "Save",
-    "saved": "Saved."
+    "saved": "Saved.",
+    "mcpLabel": "Enable the built-in MCP endpoint",
+    "mcpHint": "Master switch (default off), independent of the REST API. MCP clients connect to /api/mcp with an API token; each pond additionally opts in via its pond settings. See docs/self-hosting/public-api.md."
   }
 }

packages/shared/src/ponds.ts

@@ -43,9 +43,19 @@ export const pondSettingsSchema = z.object({
    * without it the pond and its content answer 404 through the API even
    * for a token whose user could see them in the app. */
   apiEnabled: z.boolean().default(false),
+  /** Per-pond opt-in to the built-in MCP endpoint (issue #105, default
+   * off) — independent of the REST opt-in. */
+  mcpEnabled: z.boolean().default(false),
 });
 export type PondSettings = z.infer<typeof pondSettingsSchema>;
 
+/** The machine-access surfaces a pond can opt into (issues #104/#105). */
+export type PondExposureFeature = 'api' | 'mcp';
+
+export function pondFeatureEnabled(settings: PondSettings, feature: PondExposureFeature): boolean {
+  return feature === 'api' ? settings.apiEnabled : settings.mcpEnabled;
+}
+
 export const pondNameSchema = z
   .string()
   .trim()
@@ -66,6 +76,7 @@ export const updatePondInputSchema = z
     fonts: pondFontsSchema,
     commentPolicy: z.enum(COMMENT_POLICIES),
     apiEnabled: z.boolean(),
+    mcpEnabled: z.boolean(),
   })
   .partial();
 export type UpdatePondInput = z.infer<typeof updatePondInputSchema>;

pnpm-lock.yaml

@@ -35,6 +35,9 @@ importers:
       '@dorfteich/shared':
         specifier: workspace:*
         version: link:../../packages/shared
+      '@modelcontextprotocol/sdk':
+        specifier: ^1.29.0
+        version: 1.29.0(zod@3.25.76)
       '@nestjs/common':
         specifier: ^11.0.0
         version: 11.1.27(reflect-metadata@0.2.2)(rxjs@7.8.2)
@@ -1778,6 +1781,12 @@ packages:
       y-protocols: ^1.0.6
       yjs: ^13.6.8
 
+  '@hono/node-server@1.19.14':
+    resolution: {integrity: sha512-GwtvgtXxnWsucXvbQXkRgqksiH2Qed37H9xHZocE5sA3N8O8O8/8FA3uclQXxXVzc9XBZuEOMK7+r02FmSpHtw==}
+    engines: {node: '>=18.14.1'}
+    peerDependencies:
+      hono: ^4
+
   '@hookform/resolvers@5.4.0':
     resolution: {integrity: sha512-EIsqr/t/qbinPIhGjMdtvutIN1Kk4uwbROE9/UQ93CAVGR7GkA7Y92+fX80OzXi/OB67jVFYwKGO1WzkxmkFZw==}
     peerDependencies:
@@ -1989,6 +1998,16 @@ packages:
   '@mermaid-js/parser@1.2.0':
     resolution: {integrity: sha512-oYPyv8A4As1yH5Bx+04iQEQxXuIQDe0GKCNSRgao6z8AM9jixXIfP0vsppRLvGf+nKIOb9/LdpWA4YuJiVvESA==}
 
+  '@modelcontextprotocol/sdk@1.29.0':
+    resolution: {integrity: sha512-zo37mZA9hJWpULgkRpowewez1y6ML5GsXJPY8FI0tBBCd77HEvza4jDqRKOXgHNn867PVGCyTdzqpz0izu5ZjQ==}
+    engines: {node: '>=18'}
+    peerDependencies:
+      '@cfworker/json-schema': ^4.1.1
+      zod: ^3.25 || ^4.0
+    peerDependenciesMeta:
+      '@cfworker/json-schema':
+        optional: true
+
   '@napi-rs/canvas-android-arm64@0.1.80':
     resolution: {integrity: sha512-sk7xhN/MoXeuExlggf91pNziBxLPVUqF2CAVnB57KLG/pz7+U5TKG8eXdc3pm0d7Od0WreB6ZKLj37sX9muGOQ==}
     engines: {node: '>= 10'}
@@ -3888,10 +3907,24 @@ packages:
     resolution: {integrity: sha512-mQw+2fkQbALzQ7V0MY0IqdnXNOeTtP4r0lN9z7AAawCXgqea7bDii20AYrIBrFd/Hx0M2Ocz6S111CaFkUcb0Q==}
     engines: {node: '>=0.8.x'}
 
+  eventsource-parser@3.1.0:
+    resolution: {integrity: sha512-kJezFj9YFAMLeORyi7aCLxLbD5/qWMQnoMVlVPyHIll7lgRJCc3JVln9Vgl9nwQi0YkMnhdGTMNn7CkRRAptMg==}
+    engines: {node: '>=18.0.0'}
+
+  eventsource@3.0.7:
+    resolution: {integrity: sha512-CRT1WTyuQoD771GW56XEZFQ/ZoSfWid1alKGDYMmkt2yl8UXrVR4pspqWNEcqKvVIzg6PAltWjxcSSPrboA4iA==}
+    engines: {node: '>=18.0.0'}
+
   expect-type@1.4.0:
     resolution: {integrity: sha512-KfYbmpRm0VbLjEvVa9yGwCi9GI34xvi7A/HXYWQO65CSD2u3MczUJSuwXKFIxlGsgBQizV9q5J9NHj4VG0n+pA==}
     engines: {node: '>=12.0.0'}
 
+  express-rate-limit@8.5.2:
+    resolution: {integrity: sha512-5Kb34ipNX694DH48vN9irak1Qx30nb0PLYHXfJgw4YEjiC3ZEmZJhwOp+VfiCYwFzvFTdB9QkArYS5kXa2cx2A==}
+    engines: {node: '>= 16'}
+    peerDependencies:
+      express: '>= 4.11'
+
   express@5.2.1:
     resolution: {integrity: sha512-hIS4idWWai69NezIdRt2xFVofaF4j+6INOpJlVOLDO8zXGpUVEVzIYk12UUi2JzjEzWL3IOAxcTubgz9Po0yXw==}
     engines: {node: '>= 18'}
@@ -4136,6 +4169,10 @@ packages:
   help-me@5.0.0:
     resolution: {integrity: sha512-7xgomUX6ADmcYzFik0HzAxh/73YlKR9bmFzf51CZwR+b6YtzU2m0u49hQCqV6SvlqIqsaxovfwdvbnsw3b/zpg==}
 
+  hono@4.12.29:
+    resolution: {integrity: sha512-1hNiRjawYrLq/4m3DQQjPGFg0VZkk4RjQJDff/excI6Dm9BiL75qxGrd7/c6YOxPdq6AscP3LiXhQ6fKFC1Waw==}
+    engines: {node: '>=16.9.0'}
+
   html-encoding-sniffer@4.0.0:
     resolution: {integrity: sha512-Y22oTqIU4uuPgEemfz7NDJz6OeKf12Lsu+QC+s3BVpda64lTiMYCyGwg5ki4vFxkMwQdeZDl2adZoqUgdFuTgQ==}
     engines: {node: '>=18'}
@@ -4213,6 +4250,10 @@ packages:
     resolution: {integrity: sha512-5Hh7Y1wQbvY5ooGgPbDaL5iYLAPzMTUrjMulskHLH6wnv/A+1q5rgEaiuqEjB+oxGXIVZs1FF+R/KPN3ZSQYYg==}
     engines: {node: '>=12'}
 
+  ip-address@10.2.0:
+    resolution: {integrity: sha512-/+S6j4E9AHvW9SWMSEY9Xfy66O5PWvVEJ08O0y5JGyEKQpojb0K0GKpz/v5HJ/G0vi3D2sjGK78119oXZeE0qA==}
+    engines: {node: '>= 12'}
+
   ipaddr.js@1.9.1:
     resolution: {integrity: sha512-0KI/607xoxSToH7GjN1FfSbLoU0+btTicjsQSWQlh/hZykN8KpmMf7uYwPW3R+akZ6R/w18ZlXSHBYXiYUPO3g==}
     engines: {node: '>= 0.10'}
@@ -4389,6 +4430,9 @@ packages:
     resolution: {integrity: sha512-AC/7JofJvZGrrneWNaEnJeOLUx+JlGt7tNa0wZiRPT4MY1wmfKjt2+6O2p2uz2+skll8OZZmJMNqeke7kKbNgQ==}
     hasBin: true
 
+  jose@6.2.3:
+    resolution: {integrity: sha512-YYVDInQKFJfR/xa3ojUTl8c2KoTwiL1R5Wg9YCydwH0x0B9grbzlg5HC7mMjCtUJjbQ/YnGEZIhI5tCgfTb4Hw==}
+
   joycon@3.1.1:
     resolution: {integrity: sha512-34wB/Y7MW7bzjKRjUKTa46I2Z7eV62Rkhva+KkopW7Qvv/OSWBqvkSY7vusOPrNuZcUG3tApvdVgNB8POj3SPw==}
     engines: {node: '>=10'}
@@ -4429,6 +4473,9 @@ packages:
   json-schema-traverse@1.0.0:
     resolution: {integrity: sha512-NM8/P9n3XjXhIZn1lLhkFaACTOURQXjWhV4BA/RnOv8xvgqtqpAX9IO4mRQxSx1Rlo4tqzeqb0sOlruaOy3dug==}
 
+  json-schema-typed@8.0.2:
+    resolution: {integrity: sha512-fQhoXdcvc3V28x7C7BMs4P5+kNlgUURe2jmUT1T//oBRMDrqy1QPelJimwZGo7Hg9VPV3EQV5Bnq4hbFy2vetA==}
+
   json-stable-stringify-without-jsonify@1.0.1:
     resolution: {integrity: sha512-Bdboy+l7tA3OGW6FjyFHWkP5LuByj1Tk33Ljyq0axyzdk9//JSi2u3fP1QSmd1KNwq6VOKYGlAu87CisVir6Pw==}
 
@@ -4918,6 +4965,10 @@ packages:
     resolution: {integrity: sha512-TfySrs/5nm8fQJDcBDuUng3VOUKsd7S+zqvbOTiGXHfxX4wK31ard+hoNuvkicM/2YFzlpDgABOevKSsB4G/FA==}
     engines: {node: '>= 6'}
 
+  pkce-challenge@5.0.1:
+    resolution: {integrity: sha512-wQ0b/W4Fr01qtpHlqSqspcj3EhBvimsdh0KlHhH8HRZnMsEa0ea2fTULOXOS9ccQr3om+GcGRk4e+isrZWV8qQ==}
+    engines: {node: '>=16.20.0'}
+
   pkg-types@1.3.1:
     resolution: {integrity: sha512-/Jm5M4RvtBFVkKWRu2BLUTNP8/M2a+UwuAX+ae4770q1qVGtfjG+WTCupoZixokjmHiry8uI+dlY8KXYV5HVVQ==}
 
@@ -6196,6 +6247,11 @@ packages:
     resolution: {integrity: sha512-zK7YHHz4ZXpW89AHXUPbQVGKI7uvkd3hzusTdotCg1UxyaVtg0zFJSTfW/Dq5f7OBBVnq6cZIaC8Ti4hb6dtCA==}
     engines: {node: '>= 14'}
 
+  zod-to-json-schema@3.25.2:
+    resolution: {integrity: sha512-O/PgfnpT1xKSDeQYSCfRI5Gy3hPf91mKVDuYLUHZJMiDFptvP41MSnWofm8dnCm0256ZNfZIM7DSzuSMAFnjHA==}
+    peerDependencies:
+      zod: ^3.25.28 || ^4
+
   zod@3.25.76:
     resolution: {integrity: sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==}
 
@@ -7371,6 +7427,10 @@ snapshots:
     transitivePeerDependencies:
       - srvx
 
+  '@hono/node-server@1.19.14(hono@4.12.29)':
+    dependencies:
+      hono: 4.12.29
+
   '@hookform/resolvers@5.4.0(react-hook-form@7.80.0(react@19.2.7))':
     dependencies:
       '@standard-schema/utils': 0.3.0
@@ -7583,6 +7643,28 @@ snapshots:
     dependencies:
       '@chevrotain/types': 11.1.2
 
+  '@modelcontextprotocol/sdk@1.29.0(zod@3.25.76)':
+    dependencies:
+      '@hono/node-server': 1.19.14(hono@4.12.29)
+      ajv: 8.20.0
+      ajv-formats: 3.0.1(ajv@8.20.0)
+      content-type: 1.0.5
+      cors: 2.8.6
+      cross-spawn: 7.0.6
+      eventsource: 3.0.7
+      eventsource-parser: 3.1.0
+      express: 5.2.1
+      express-rate-limit: 8.5.2(express@5.2.1)
+      hono: 4.12.29
+      jose: 6.2.3
+      json-schema-typed: 8.0.2
+      pkce-challenge: 5.0.1
+      raw-body: 3.0.2
+      zod: 3.25.76
+      zod-to-json-schema: 3.25.2(zod@3.25.76)
+    transitivePeerDependencies:
+      - supports-color
+
   '@napi-rs/canvas-android-arm64@0.1.80':
     optional: true
 
@@ -8589,6 +8671,10 @@ snapshots:
     optionalDependencies:
       ajv: 8.18.0
 
+  ajv-formats@3.0.1(ajv@8.20.0):
+    optionalDependencies:
+      ajv: 8.20.0
+
   ajv-keywords@3.5.2(ajv@6.15.0):
     dependencies:
       ajv: 6.15.0
@@ -9683,8 +9769,19 @@ snapshots:
 
   events@3.3.0: {}
 
+  eventsource-parser@3.1.0: {}
+
+  eventsource@3.0.7:
+    dependencies:
+      eventsource-parser: 3.1.0
+
   expect-type@1.4.0: {}
 
+  express-rate-limit@8.5.2(express@5.2.1):
+    dependencies:
+      express: 5.2.1
+      ip-address: 10.2.0
+
   express@5.2.1:
     dependencies:
       accepts: 2.0.0
@@ -9983,6 +10080,8 @@ snapshots:
 
   help-me@5.0.0: {}
 
+  hono@4.12.29: {}
+
   html-encoding-sniffer@4.0.0:
     dependencies:
       whatwg-encoding: 3.1.1
@@ -10058,6 +10157,8 @@ snapshots:
 
   internmap@2.0.3: {}
 
+  ip-address@10.2.0: {}
+
   ipaddr.js@1.9.1: {}
 
   is-array-buffer@3.0.5:
@@ -10224,6 +10325,8 @@ snapshots:
 
   jiti@2.7.0: {}
 
+  jose@6.2.3: {}
+
   joycon@3.1.1: {}
 
   js-tokens@4.0.0: {}
@@ -10271,6 +10374,8 @@ snapshots:
 
   json-schema-traverse@1.0.0: {}
 
+  json-schema-typed@8.0.2: {}
+
   json-stable-stringify-without-jsonify@1.0.1: {}
 
   json5@2.2.3: {}
@@ -10745,6 +10850,8 @@ snapshots:
 
   pirates@4.0.7: {}
 
+  pkce-challenge@5.0.1: {}
+
   pkg-types@1.3.1:
     dependencies:
       confbox: 0.1.8
@@ -12192,6 +12299,10 @@ snapshots:
       compress-commons: 6.0.2
       readable-stream: 4.7.0
 
+  zod-to-json-schema@3.25.2(zod@3.25.76):
+    dependencies:
+      zod: 3.25.76
+
   zod@3.25.76: {}
 
   zod@4.4.3: {}