v1.14.1-mcp-poc: single-server MCP client against Context7

Validates the MCP-client loop end-to-end against one real MCP server before
the full v1.15 port. New services/mcp-client.ts wraps @modelcontextprotocol/sdk
v1.29.0 with Streamable HTTP transport. On startup (when MCP_CONTEXT7_URL is
set), connects to Context7, discovers tools via tools/list, wraps each as a
ToolDef prefixed context7_<name>, and appends to ALL_TOOLS via appendMcpTools.

Read-only invariant guard rejects any tool with readOnlyHint: false. Tool
dispatch is transparent — executeToolCall routes MCP calls through the ToolDef
execute wrapper, which strips the prefix before calling the MCP server. Result
size capped at 5MB with truncation. Graceful degradation: server down at
startup → zero tools; server down mid-session → error result, model
self-corrects.

Adversarial review caught that a Zod .default() on the URL config made MCP
always-on instead of opt-in — fixed by removing the default. MCP_CONTEXT7_URL
must be explicitly set to enable.

ALL_TOOLS changed from ReadonlyArray to mutable to support late-registration.
appendMcpTools re-sorts and rebuilds TOOLS_BY_NAME after append.

348/348 server tests passing (16 new mcp-client tests). No schema changes,
no frontend changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/server/src/services/__tests__/mcp-client.test.ts

@@ -0,0 +1,141 @@
+/**
+ * v1.14.1-mcp-poc: unit tests for the MCP client service.
+ * Pure unit tests — no live MCP server needed. Tests the tool-wrapping,
+ * read-only guard, name prefixing, content extraction, and error handling.
+ */
+import { describe, it, expect } from 'vitest';
+import { wrapMcpTool, extractContent, isToolReadOnly } from '../mcp-client.js';
+
+describe('mcp-client', () => {
+  describe('wrapMcpTool', () => {
+    it('produces a ToolDef with context7_ prefix', () => {
+      const mcpTool = {
+        name: 'resolve-library-id',
+        description: 'Resolve a library identifier',
+        inputSchema: {
+          type: 'object' as const,
+          properties: { query: { type: 'string' } },
+          required: ['query'],
+        },
+      };
+
+      const wrapped = wrapMcpTool(mcpTool);
+
+      expect(wrapped.name).toBe('context7_resolve-library-id');
+      expect(wrapped.description).toBe('Resolve a library identifier');
+      expect(wrapped.jsonSchema.type).toBe('function');
+      expect(wrapped.jsonSchema.function.name).toBe('context7_resolve-library-id');
+      expect(wrapped.jsonSchema.function.parameters).toEqual(mcpTool.inputSchema);
+      expect(typeof wrapped.execute).toBe('function');
+    });
+
+    it('defaults description to empty string when absent', () => {
+      const mcpTool = {
+        name: 'no-desc',
+        inputSchema: { type: 'object' as const, properties: {} },
+      };
+
+      const wrapped = wrapMcpTool(mcpTool);
+
+      expect(wrapped.description).toBe('');
+      expect(wrapped.jsonSchema.function.description).toBe('');
+    });
+
+    it('uses passthrough Zod schema (z.record)', () => {
+      const mcpTool = {
+        name: 'test',
+        inputSchema: { type: 'object' as const, properties: {} },
+      };
+
+      const wrapped = wrapMcpTool(mcpTool);
+
+      // z.record(z.unknown()) should accept any object
+      const result = wrapped.inputSchema.safeParse({ foo: 'bar', baz: 123 });
+      expect(result.success).toBe(true);
+    });
+  });
+
+  describe('isToolReadOnly', () => {
+    it('accepts tools with readOnlyHint: true', () => {
+      expect(isToolReadOnly({ readOnlyHint: true })).toBe(true);
+    });
+
+    it('accepts tools with no annotations', () => {
+      expect(isToolReadOnly(undefined)).toBe(true);
+    });
+
+    it('accepts tools with empty annotations', () => {
+      expect(isToolReadOnly({})).toBe(true);
+    });
+
+    it('rejects tools with readOnlyHint: false', () => {
+      expect(isToolReadOnly({ readOnlyHint: false })).toBe(false);
+    });
+
+    it('accepts tools with only destructiveHint set', () => {
+      // readOnlyHint is not set, so it should be accepted per D3
+      expect(isToolReadOnly({ destructiveHint: true })).toBe(true);
+    });
+  });
+
+  describe('extractContent', () => {
+    it('extracts single text block', () => {
+      const content = [{ type: 'text', text: 'hello world' }];
+      expect(extractContent(content)).toBe('hello world');
+    });
+
+    it('joins multiple text blocks with newline', () => {
+      const content = [
+        { type: 'text', text: 'line 1' },
+        { type: 'text', text: 'line 2' },
+      ];
+      expect(extractContent(content)).toBe('line 1\nline 2');
+    });
+
+    it('returns "(no output)" for empty content', () => {
+      expect(extractContent([])).toBe('(no output)');
+    });
+
+    it('returns "(no output)" for undefined content', () => {
+      expect(extractContent(undefined)).toBe('(no output)');
+    });
+
+    it('serializes non-text blocks as JSON', () => {
+      const content = [
+        { type: 'resource', uri: 'file:///foo', mimeType: 'text/plain' },
+      ];
+      const result = extractContent(content);
+      expect(result).toContain('"type":"resource"');
+      expect(result).toContain('"uri":"file:///foo"');
+    });
+
+    it('returns error shape when isError is true', () => {
+      const content = [{ type: 'text', text: 'something failed' }];
+      const result = extractContent(content, true);
+      expect(result).toEqual({ error: true, output: 'something failed' });
+    });
+
+    it('returns error shape with joined content on isError', () => {
+      const content = [
+        { type: 'text', text: 'error 1' },
+        { type: 'text', text: 'error 2' },
+      ];
+      const result = extractContent(content, true);
+      expect(result).toEqual({ error: true, output: 'error 1\nerror 2' });
+    });
+  });
+
+  describe('name prefix', () => {
+    it('prefixed name maps correctly in wrapped tool', () => {
+      const mcpTool = {
+        name: 'query-docs',
+        description: 'Query documentation',
+        inputSchema: { type: 'object' as const, properties: {} },
+      };
+
+      const wrapped = wrapMcpTool(mcpTool);
+      expect(wrapped.name).toBe('context7_query-docs');
+      expect(wrapped.jsonSchema.function.name).toBe('context7_query-docs');
+    });
+  });
+});