feat(gateway): MCP client — connect to external MCP servers as agent tools (#127) (#141)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/agent/agent.module.ts

@@ -5,10 +5,11 @@ import { RoutingService } from './routing.service.js';
 import { ProvidersController } from './providers.controller.js';
 import { SessionsController } from './sessions.controller.js';
 import { CoordModule } from '../coord/coord.module.js';
+import { McpClientModule } from '../mcp-client/mcp-client.module.js';
 
 @Global()
 @Module({
-  imports: [CoordModule],
+  imports: [CoordModule, McpClientModule],
   providers: [ProviderService, RoutingService, AgentService],
   controllers: [ProvidersController, SessionsController],
   exports: [AgentService, ProviderService, RoutingService],

apps/gateway/src/agent/agent.service.ts

@@ -13,6 +13,7 @@ import { MEMORY } from '../memory/memory.tokens.js';
 import { EmbeddingService } from '../memory/embedding.service.js';
 import { CoordService } from '../coord/coord.service.js';
 import { ProviderService } from './provider.service.js';
+import { McpClientService } from '../mcp-client/mcp-client.service.js';
 import { createBrainTools } from './tools/brain-tools.js';
 import { createCoordTools } from './tools/coord-tools.js';
 import { createMemoryTools } from './tools/memory-tools.js';
@@ -53,6 +54,7 @@ export class AgentService implements OnModuleDestroy {
     @Inject(MEMORY) private readonly memory: Memory,
     @Inject(EmbeddingService) private readonly embeddingService: EmbeddingService,
     @Inject(CoordService) private readonly coordService: CoordService,
+    @Inject(McpClientService) private readonly mcpClientService: McpClientService,
   ) {
     const fileBaseDir = process.env['AGENT_FILE_SANDBOX_DIR'] ?? process.cwd();
     const gitDefaultCwd = process.env['AGENT_GIT_CWD'] ?? process.cwd();
@@ -96,6 +98,13 @@ export class AgentService implements OnModuleDestroy {
       `Creating agent session: ${sessionId} (provider=${providerName}, model=${modelId})`,
     );
 
+    // Combine static tools with dynamically discovered MCP client tools
+    const mcpTools = this.mcpClientService.getToolDefinitions();
+    const allCustomTools = [...this.customTools, ...mcpTools];
+    if (mcpTools.length > 0) {
+      this.logger.log(`Attaching ${mcpTools.length} MCP client tool(s) to session ${sessionId}`);
+    }
+
     let piSession: PiAgentSession;
     try {
       const result = await createAgentSession({
@@ -103,7 +112,7 @@ export class AgentService implements OnModuleDestroy {
         modelRegistry: this.providerService.getRegistry(),
         model: model ?? undefined,
         tools: [],
-        customTools: this.customTools,
+        customTools: allCustomTools,
       });
       piSession = result.session;
     } catch (err) {