ExpressJS MCP

# Example 04: Separate MCP Server This example demonstrates running the MCP server as a standalone HTTP gateway, separate from the main Express application. ## Architecture ``` ┌─────────────┐ ┌──────────────┐ ┌──────────────┐ │ MCP Clients │────▶│ MCP Gateway │────▶│ Express App │ │ │ │ (port 7878) │ │ (port 3004) │ └─────────────┘ └──────────────┘ └──────────────┘ HTTP In-Memory Dispatch ``` ## Features - **Separate Ports**: Main app and MCP gateway on different ports - **In-Memory Dispatch**: No network overhead between servers - **Independent Scaling**: Scale MCP gateway separately - **Security Isolation**: Different security policies per server ## Running the Example ```bash # Install dependencies pnpm install # Run the example pnpm tsx examples/04-separate-server/server.ts # Or with custom ports APP_PORT=8080 MCP_PORT=9090 pnpm tsx examples/04-separate-server/server.ts ``` ## Testing 1. **Direct API Access** (port 3004): ```bash # Regular API call curl http://localhost:3004/items # Create item directly curl -X POST http://localhost:3004/items \ -H "Content-Type: application/json" \ -d '{"name": "Direct Item", "price": 29.99}' ``` 2. **MCP Gateway Access** (port 7878): ```bash # List MCP tools curl http://localhost:7878/mcp/tools # Invoke via MCP curl -X POST http://localhost:7878/mcp/invoke \ -H "Content-Type: application/json" \ -d '{ "toolName": "GET_/items", "args": {} }' ``` ## Use Cases ### Microservices Architecture ```typescript // API Gateway const apiGateway = express(); apiGateway.use("/api", proxy("http://api-service:3000")); // MCP Gateway for all services const mcp = new ExpressMCP(apiGateway); await mcp.startStandalone({ port: 7878 }); ``` ### Load Balancing ```nginx # nginx.conf upstream app_servers { server app1:3004; server app2:3004; } upstream mcp_servers { server mcp1:7878; server mcp2:7878; } ``` ### Security Isolation ```typescript // Main app - internal network only app.listen(3004, "127.0.0.1"); // MCP gateway - public facing with auth const mcp = new ExpressMCP(app, { auth: { enabled: true } }); await mcp.startStandalone({ port: 7878 }); ``` ## Benefits 1. **Separation of Concerns**: MCP protocol handling separate from business logic 2. **Independent Deployment**: Update MCP gateway without touching main app 3. **Performance**: Different optimization strategies per server 4. **Monitoring**: Separate metrics for API vs MCP traffic ## Configuration Environment variables: - `APP_PORT`: Main application port (default: 3004) - `MCP_PORT`: MCP gateway port (default: 7878) ## Next Steps - See [Example 05](../05-dynamic-tools) for dynamic tool registration - See [Example 06](../06-custom-router) for custom MCP routing - See [Example 08](../08-auth-token) for authentication