05-mcp-server

05-mcp-server — MCP Tools Example

This is a complete, standalone example of exposing your RustAPI endpoints as MCP tools for LLMs and AI agents (Claude, Cursor, Continue, custom agents, etc.).

Features Demonstrated

• RustApi::auto() for zero-boilerplate routing + OpenAPI
• Tagging routes with #[rustapi_rs::tag("agent")] to selectively expose them
• McpServer::from_rustapi(...) with InvocationMode::InProcess (zero network overhead, full pipeline respect)
• Side-by-side HTTP API (port 8080) + MCP server (port 9090)
• Graceful shutdown via run_rustapi_and_mcp_with_shutdown
• Security: untagged routes (e.g. /admin/secret) are never visible to agents

Run

# From the rustapi-rs-examples root
cargo run -p mcp-server

Output:

🚀 HTTP API:  http://127.0.0.1:8080
🧠 MCP tools: http://127.0.0.1:9090

Usage

Normal HTTP (for humans / browsers)

• GET http://127.0.0.1:8080/weather/Istanbul
• POST http://127.0.0.1:8080/calc/sum with {"a": 40, "b": 2}

MCP / Agent endpoint (port 9090)

Point any MCP client at http://127.0.0.1:9090 (HTTP + SSE transport).

Manual test with curl (JSON-RPC):

# initialize
curl -X POST http://127.0.0.1:9090 \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize"}'

# list tools (only the ones with "agent" tag)
curl -X POST http://127.0.0.1:9090 \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/list"}'

# call a tool
curl -X POST http://127.0.0.1:9090 \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"get_weather","arguments":{"city":"Istanbul"}}}'

How It Works

Routes annotated with #[rustapi_rs::tag("agent")] are automatically turned into MCP tools using the OpenAPI schema RustAPI already generates.

InvocationMode::InProcess means:

• Tool calls bypass the network entirely
• Still go through validation, extractors, middleware, error handlers, etc.
• Extremely fast (~microseconds)

See source in src/main.rs.

See Also

• Main RustAPI repo examples: crates/rustapi-rs/examples/mcp_tools.rs (quick in-tree demo)
• Cookbook: MCP Integration
• Other MCP recipes in the cookbook (in-process, OpenAPI CLI, stdio)
• The full rustapi-rs-examples repository

Dependencies (in this example)

rustapi-rs = { version = "0.1.507", features = ["protocol-mcp", "swagger-ui"] }

License

Same as the main RustAPI project (MIT OR Apache-2.0).