diff --git a/dashcaddy-api/__tests__/mcp/mcp-core-dc166.test.js b/dashcaddy-api/__tests__/mcp/mcp-core-dc166.test.js
new file mode 100644
index 0000000..efdf20c
--- /dev/null
+++ b/dashcaddy-api/__tests__/mcp/mcp-core-dc166.test.js
@@ -0,0 +1,195 @@
+/**
+ * DC-166: MCP control-plane completion — 11 new tools (28 total).
+ * Proves: tool catalog integrity (names unique/aligned with handlers),
+ * each new handler hits the RIGHT method+path+body (captured fetchImpl),
+ * calendar days->ISO window translation, security summary fan-out,
+ * DNS delete query construction, and credential passthrough on writes.
+ */
+
+'use strict';
+
+const { TOOLS, createToolHandler } = require('../../src/mcp/mcp-core');
+
+function harness(handlerOpts = {}) {
+  const calls = [];
+  const fetchImpl = async (url, opts) => {
+    calls.push({ url, method: opts.method, headers: opts.headers, body: opts.body ? JSON.parse(opts.body) : undefined });
+    return { ok: true, status: 200, text: async () => JSON.stringify({ success: true, echo: calls[calls.length - 1] }) };
+  };
+  const handleTool = createToolHandler({
+    baseUrl: 'http://127.0.0.1:1',
+    apiKey: 'dk_' + 'test_key',
+    fetchImpl,
+    ...handlerOpts,
+  });
+  return { calls, handleTool };
+}
+
+const NEW_TOOLS = [
+  'dashcaddy_calendar_events', 'dashcaddy_calendar_add_source',
+  'dashcaddy_security_events', 'dashcaddy_security_summary',
+  'dashcaddy_license_status', 'dashcaddy_capabilities',
+  'dashcaddy_dns_add_record', 'dashcaddy_dns_remove_record',
+  'dashcaddy_deploy_recipe', 'dashcaddy_run_workflow',
+  'dashcaddy_tailscale_status',
+];
+
+describe('DC-166 tool catalog', () => {
+  test('all 11 new tools declared, total 28, names unique', () => {
+    const names = TOOLS.map((t) => t.name);
+    for (const n of NEW_TOOLS) expect(names).toContain(n);
+    expect(names.length).toBe(28);
+    expect(new Set(names).size).toBe(28);
+  });
+
+  test('every tool has description + object inputSchema', () => {
+    for (const t of TOOLS) {
+      expect(typeof t.description).toBe('string');
+      expect(t.description.length).toBeGreaterThan(10);
+      expect(t.inputSchema.type).toBe('object');
+    }
+  });
+
+  test('required fields declared on write tools', () => {
+    const byName = Object.fromEntries(TOOLS.map((t) => [t.name, t]));
+    expect(byName.dashcaddy_dns_add_record.inputSchema.required).toEqual(['domain', 'ip']);
+    expect(byName.dashcaddy_deploy_recipe.inputSchema.required).toEqual(['recipeId']);
+    expect(byName.dashcaddy_run_workflow.inputSchema.required).toEqual(['workflowId']);
+    expect(byName.dashcaddy_calendar_add_source.inputSchema.required).toEqual(['name', 'type', 'url']);
+    expect(byName.dashcaddy_calendar_add_source.inputSchema.properties.type.enum).toEqual(['caldav', 'ics']);
+  });
+});
+
+describe('DC-166 handler routing (captured fetchImpl)', () => {
+  test('calendar_events translates days into ISO start/end window', async () => {
+    const { calls, handleTool } = harness();
+    const before = Date.now();
+    await handleTool('dashcaddy_calendar_events', { days: 7 });
+    expect(calls).toHaveLength(1);
+    expect(calls[0].method).toBe('GET');
+    const u = new URL(calls[0].url);
+    expect(u.pathname).toBe('/api/v1/calendar/events');
+    const start = new Date(u.searchParams.get('start'));
+    const end = new Date(u.searchParams.get('end'));
+    expect(Math.abs(start.getTime() - before)).toBeLessThan(60000);
+    expect(end - start).toBeGreaterThanOrEqual(6 * 3600e3);
+    expect(end - start).toBeLessThanOrEqual(7 * 86400e3 + 60000);
+  });
+
+  test('calendar_events defaults to 14 days and clamps to 60', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_calendar_events', {});
+    const u0 = new URL(calls[0].url);
+    const span0 = new Date(u0.searchParams.get('end')) - new Date(u0.searchParams.get('start'));
+    expect(Math.round(span0 / 86400e3)).toBe(14);
+    await handleTool('dashcaddy_calendar_events', { days: 999 });
+    const u = new URL(calls[1].url);
+    const span = new Date(u.searchParams.get('end')) - new Date(u.searchParams.get('start'));
+    expect(Math.round(span / 86400e3)).toBe(60);
+  });
+
+  test('calendar_add_source posts credentials through, omits absent fields', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_calendar_add_source', { name: 'P', type: 'caldav', url: 'https://c.example/dav', user: 'u1', pass: 'p1' });
+    await handleTool('dashcaddy_calendar_add_source', { name: 'F', type: 'ics', url: 'https://f.example/a.ics' });
+    expect(calls[0].method).toBe('POST');
+    expect(calls[0].url).toBe('http://127.0.0.1:1/api/v1/calendar/sources');
+    expect(calls[0].body).toEqual({ name: 'P', type: 'caldav', url: 'https://c.example/dav', user: 'u1', pass: 'p1' });
+    expect(calls[1].body.user).toBeUndefined();
+    expect(calls[1].body.pass).toBeUndefined();
+  });
+
+  test('security_events passes only provided filters as query string', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_security_events', { limit: 5, severity: 'critical' });
+    await handleTool('dashcaddy_security_events', {});
+    const u1 = new URL(calls[0].url);
+    expect(u1.pathname).toBe('/api/v1/security/events');
+    expect(u1.searchParams.get('limit')).toBe('5');
+    expect(u1.searchParams.get('severity')).toBe('critical');
+    expect(u1.searchParams.get('source_type')).toBeNull();
+    expect(calls[1].url).toBe('http://127.0.0.1:1/api/v1/security/events');
+  });
+
+  test('security_summary fans out stats+perimeter, respects withPerimeter false', async () => {
+    const { calls, handleTool } = harness();
+    const r1 = await handleTool('dashcaddy_security_summary', {});
+    expect(calls.map(c => c.url)).toEqual([
+      'http://127.0.0.1:1/api/v1/security/events/stats',
+      'http://127.0.0.1:1/api/v1/security/events/perimeter',
+    ]);
+    expect(r1.stats).toBeDefined();
+    expect(r1.perimeter).toBeDefined();
+    calls.length = 0;
+    const r2 = await handleTool('dashcaddy_security_summary', { withPerimeter: false });
+    expect(calls).toHaveLength(1);
+    expect(r2.success).toBe(true);
+  });
+
+  test('license_status and capabilities read the right endpoints', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_license_status', {});
+    await handleTool('dashcaddy_capabilities', {});
+    expect(calls[0].url).toBe('http://127.0.0.1:1/api/v1/license/status');
+    expect(calls[0].method).toBe('GET');
+    expect(calls[1].url).toBe('http://127.0.0.1:1/api/v1/capabilities');
+  });
+
+  test('dns_add_record posts the provider schema body', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_dns_add_record', { domain: 'x.home.example', ip: '10.0.0.5', ttl: 300 });
+    expect(calls[0].method).toBe('POST');
+    expect(calls[0].url).toBe('http://127.0.0.1:1/api/v1/dns/record');
+    expect(calls[0].body).toEqual({ domain: 'x.home.example', ip: '10.0.0.5', ttl: 300 });
+    await handleTool('dashcaddy_dns_add_record', { domain: 'y.home.example', ip: '10.0.0.6' });
+    expect(calls[1].body.ttl).toBeUndefined();
+  });
+
+  test('dns_remove_record deletes with encoded query, type defaults A', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_dns_remove_record', { domain: 'a b.example', type: 'CNAME' });
+    await handleTool('dashcaddy_dns_remove_record', { domain: 'z.example', ipAddress: '1.2.3.4' });
+    expect(calls[0].method).toBe('DELETE');
+    const u0 = new URL(calls[0].url);
+    expect(u0.pathname).toBe('/api/v1/dns/record');
+    expect(u0.searchParams.get('domain')).toBe('a b.example');
+    expect(u0.searchParams.get('type')).toBe('CNAME');
+    const u1 = new URL(calls[1].url);
+    expect(u1.searchParams.get('type')).toBe('A');
+    expect(u1.searchParams.get('ipAddress')).toBe('1.2.3.4');
+  });
+
+  test('deploy_recipe maps overrides to config body', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_deploy_recipe', { recipeId: 'media-stack', overrides: { plex: { port: 32400 } } });
+    expect(calls[0].method).toBe('POST');
+    expect(calls[0].url).toBe('http://127.0.0.1:1/api/v1/recipes/deploy');
+    expect(calls[0].body).toEqual({ recipeId: 'media-stack', config: { plex: { port: 32400 } } });
+    await handleTool('dashcaddy_deploy_recipe', { recipeId: 'x' });
+    expect(calls[1].body.config).toBeUndefined();
+  });
+
+  test('run_workflow posts encoded id to /run, tailscale_status reads status', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_run_workflow', { workflowId: 'disk space alert' });
+    expect(calls[0].method).toBe('POST');
+    expect(decodeURIComponent(calls[0].url)).toBe('http://127.0.0.1:1/api/v1/workflows/disk space alert/run');
+    expect(calls[0].url).toContain('disk%20space%20alert');
+    await handleTool('dashcaddy_tailscale_status', {});
+    expect(calls[1].url).toBe('http://127.0.0.1:1/api/v1/tailscale/status');
+    expect(calls[1].method).toBe('GET');
+  });
+
+  test('credential passthrough preserved on the new write tools (x-api-key)', async () => {
+    const { calls, handleTool } = harness();
+    await handleTool('dashcaddy_dns_add_record', { domain: 'w.example', ip: '1.1.1.1' });
+    expect(calls[0].headers['x-api-key']).toBe('dk_' + 'test_key');
+  });
+
+  test('unknown tool still rejected after catalog extension', async () => {
+    const { handleTool } = harness();
+    const r = await handleTool('dashcaddy_delete_everything', {});
+    expect(r.error).toBe(true);
+    expect(r.message).toMatch(/Unknown tool/);
+  });
+});
diff --git a/dashcaddy-api/src/mcp/mcp-core.js b/dashcaddy-api/src/mcp/mcp-core.js
index 5e602d1..92b047e 100644
--- a/dashcaddy-api/src/mcp/mcp-core.js
+++ b/dashcaddy-api/src/mcp/mcp-core.js
@@ -192,6 +192,122 @@ const TOOLS = [
     description: 'List all hosts in the DashCaddy fleet (for multi-server management).',
     inputSchema: { type: 'object', properties: {} },
   },
+  // ── Calendar (DC-166) ──
+  {
+    name: 'dashcaddy_calendar_events',
+    description: 'List upcoming calendar events from configured sources (shared with the dashboard calendar widget). Useful for "what is on my schedule this week?"',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        days: { type: 'number', description: 'Horizon in days from now (default 14, max 60)' },
+      },
+    },
+  },
+  {
+    name: 'dashcaddy_calendar_add_source',
+    description: 'Add a calendar source: a CalDAV URL with user/pass or token, or a read-only ICS feed URL. DashCaddy-deployed Radicale servers auto-register themselves; this is for external calendars.',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        name: { type: 'string', description: 'Display name (e.g. "Personal")' },
+        type: { type: 'string', enum: ['caldav', 'ics'], description: 'Source type' },
+        url: { type: 'string', description: 'CalDAV base URL or .ics feed URL (https required)' },
+        user: { type: 'string', description: 'CalDAV username (caldav only)' },
+        pass: { type: 'string', description: 'CalDAV password (caldav only)' },
+      },
+      required: ['name', 'type', 'url'],
+    },
+  },
+  // ── Security Center (DC-166) ──
+  {
+    name: 'dashcaddy_security_events',
+    description: 'Query the unified Security Center event pipeline (docker/caddy/dns/tailscale/audit/health sources, PII-masked). Useful for "any suspicious activity?" or "recent auth failures".',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        limit: { type: 'number', description: 'Max events (default 20)' },
+        source_type: { type: 'string', description: 'Filter by source (caddy, docker, dns, tailscale, audit, health…)' },
+        severity: { type: 'string', description: 'Filter by severity (info, warning, error, critical)' },
+        since: { type: 'string', description: 'ISO datetime lower bound (optional)' },
+      },
+    },
+  },
+  {
+    name: 'dashcaddy_security_summary',
+    description: 'Security Center aggregate stats plus per-IP/per-vhost perimeter analytics. Useful for "which IPs are attacking me?"',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        withPerimeter: { type: 'boolean', description: 'Include perimeter rollups (default true)' },
+      },
+    },
+  },
+  // ── License + capabilities (DC-166) ──
+  {
+    name: 'dashcaddy_license_status',
+    description: 'License status: active/inactive, tier, lifetime flag, days remaining, granted premium features, and the gated-feature catalog.',
+    inputSchema: { type: 'object', properties: {} },
+  },
+  {
+    name: 'dashcaddy_capabilities',
+    description: 'Machine-readable capability manifest of the running build: version, app-template count + categories, MCP tool list, premium feature list, language count. Ground truth for "what can this DashCaddy do?"',
+    inputSchema: { type: 'object', properties: {} },
+  },
+  // ── DNS write (DC-166) ──
+  {
+    name: 'dashcaddy_dns_add_record',
+    description: 'Create a DNS A record via the configured DNS provider (Technitium/universal). Points a hostname at a machine without touching the dashboard.',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        domain: { type: 'string', description: 'FQDN or hostname to add (e.g. "printer.home.example.com")' },
+        ip: { type: 'string', description: 'IPv4 address for the A record' },
+        ttl: { type: 'number', description: 'TTL seconds (optional, provider default)' },
+      },
+      required: ['domain', 'ip'],
+    },
+  },
+  {
+    name: 'dashcaddy_dns_remove_record',
+    description: 'Delete a DNS record via the configured provider. Pass the identifying fields that dashcaddy_list_dns returned (domain, type, ipAddress).',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        domain: { type: 'string', description: 'Record name (e.g. "printer.home.example.com")' },
+        type: { type: 'string', description: 'Record type (A, CNAME…; default A)' },
+        ipAddress: { type: 'string', description: 'Record data (IP) to disambiguate' },
+      },
+      required: ['domain'],
+    },
+  },
+  // ── Recipes & workflows (DC-166) ──
+  {
+    name: 'dashcaddy_deploy_recipe',
+    description: 'Deploy a multi-container Recipe stack (premium) by recipe id with optional per-service overrides. List ids via dashcaddy_search_catalog-style GET /api/v1/recipes/templates.',
+    inputSchema: {
+      type: 'object',
+      properties: {
+        recipeId: { type: 'string', description: 'Recipe id (e.g. "media-stack")' },
+        overrides: { type: 'object', description: 'Per-service config overrides (optional)', additionalProperties: true },
+      },
+      required: ['recipeId'],
+    },
+  },
+  {
+    name: 'dashcaddy_run_workflow',
+    description: 'Run a bundled maintenance workflow (premium): auto-restart-on-crash, backup-before-update, health-check-on-interval, disk-space-alert, weekly-container-report.',
+    inputSchema: {
+      type: 'object',
+      properties: { workflowId: { type: 'string', description: 'Workflow id' } },
+      required: ['workflowId'],
+    },
+  },
+  // ── Tailscale (DC-166) ──
+  {
+    name: 'dashcaddy_tailscale_status',
+    description: 'Tailscale integration status and enrolled devices (when the Tailscale feature is configured). Useful for checking VPN coverage of tailnet-only services.',
+    inputSchema: { type: 'object', properties: {} },
+  },
 ];
 
 const RESOURCES = [
@@ -424,6 +540,84 @@ function createToolHandler({ baseUrl, apiKey, headers, fetchImpl, log }) {
         return apiCall('GET', '/fleet/hosts');
       }
 
+      // ── Calendar (DC-166) ──
+      case 'dashcaddy_calendar_events': {
+        // Route contract (routes/calendar.js): ISO start/end, capped 400-day
+        // range. Translate the friendlier `days` horizon into that shape.
+        const days = Math.min(Math.max(Number(args.days) || 14, 1), 60);
+        const from = new Date();
+        const to = new Date(from.getTime() + days * 86400000);
+        const p = `/calendar/events?start=${encodeURIComponent(from.toISOString())}&end=${encodeURIComponent(to.toISOString())}`;
+        return apiCall('GET', p);
+      }
+
+      case 'dashcaddy_calendar_add_source': {
+        return apiCall('POST', '/calendar/sources', {
+          name: args.name, type: args.type, url: args.url,
+          ...(args.user ? { user: args.user } : {}),
+          ...(args.pass ? { pass: args.pass } : {}),
+        });
+      }
+
+      // ── Security Center (DC-166) ──
+      case 'dashcaddy_security_events': {
+        const qs = new URLSearchParams();
+        for (const k of ['limit', 'source_type', 'severity', 'since']) {
+          if (args[k] !== undefined && args[k] !== null) qs.set(k, String(args[k]));
+        }
+        const q = qs.toString();
+        return apiCall('GET', `/security/events${q ? `?${q}` : ''}`);
+      }
+
+      case 'dashcaddy_security_summary': {
+        const stats = await apiCall('GET', '/security/events/stats');
+        if (args.withPerimeter === false) return stats;
+        const peri = await apiCall('GET', '/security/events/perimeter');
+        return { stats, perimeter: peri };
+      }
+
+      // ── License + capabilities (DC-166) ──
+      case 'dashcaddy_license_status': {
+        return apiCall('GET', '/license/status');
+      }
+
+      case 'dashcaddy_capabilities': {
+        return apiCall('GET', '/capabilities');
+      }
+
+      // ── DNS write (DC-166) ──
+      case 'dashcaddy_dns_add_record': {
+        return apiCall('POST', '/dns/record', {
+          domain: args.domain, ip: args.ip,
+          ...(args.ttl !== undefined ? { ttl: args.ttl } : {}),
+        });
+      }
+
+      case 'dashcaddy_dns_remove_record': {
+        const qs = new URLSearchParams();
+        qs.set('domain', String(args.domain));
+        qs.set('type', String(args.type || 'A'));
+        if (args.ipAddress !== undefined) qs.set('ipAddress', String(args.ipAddress));
+        return apiCall('DELETE', `/dns/record?${qs.toString()}`);
+      }
+
+      // ── Recipes & workflows (DC-166) ──
+      case 'dashcaddy_deploy_recipe': {
+        return apiCall('POST', '/recipes/deploy', {
+          recipeId: args.recipeId,
+          ...(args.overrides ? { config: args.overrides } : {}),
+        });
+      }
+
+      case 'dashcaddy_run_workflow': {
+        return apiCall('POST', `/workflows/${encodeURIComponent(args.workflowId)}/run`, {});
+      }
+
+      // ── Tailscale (DC-166) ──
+      case 'dashcaddy_tailscale_status': {
+        return apiCall('GET', '/tailscale/status');
+      }
+
       default:
         return { error: true, message: `Unknown tool: ${name}` };
     }
@@ -462,6 +656,7 @@ function createMcpHandler({ handleTool, serverVersion }) {
         };
       }
 
+
       case 'tools/list': {
         return {
           jsonrpc: '2.0',