rust

Rust Examples

TodoService MCP server examples in Rust, demonstrating all supported transports.

Prerequisites

• Rust 1.93.0+ (stable; edition 2024)
• Generated code already in proto/generated/rust/ (run buf generate from examples/)

The generated code includes both TodoService (todo/v1/) and CounterService (counter/v1/); the Rust examples use TodoService.

Structure

rust/
├── Cargo.toml         # Lib + 3 binary targets
└── src/
    ├── lib.rs         # Re-exports shared modules
    ├── proto.rs       # Prost includes for todo.v1
    ├── impl.rs        # Shared TodoServer (gRPC + MCP impls)
    └── bin/
        ├── http.rs    # streamable-http + gRPC side-by-side
        ├── stdio.rs   # stdio transport (for Claude Desktop)
        └── sse.rs     # SSE transport (legacy)

The impl.rs module contains the TodoServer struct with both the tonic TodoService trait impl (gRPC) and the generated TodoServiceMcpServer trait impl (MCP JSON ↔ prost bridge). All three binaries share it via the library crate.

Building

cd examples/rust
cargo build

This produces three binaries: http, stdio, and sse.

Running

Streamable HTTP (+ gRPC)

cargo run --bin http
# gRPC  → [::]:50051 (reflection enabled)
# MCP   → 0.0.0.0:8082 (streamable-http)

Environment variables:

• MCP_HOST — bind address (default 0.0.0.0)
• MCP_PORT — MCP port (default 8082)

Stdio

cargo run --bin stdio
# MCP communicates over stdin/stdout

For MCP Inspector:

cargo build --bin stdio
npx @modelcontextprotocol/inspector -- ./target/debug/stdio

SSE

cargo run --bin sse
# MCP → 0.0.0.0:8083 (SSE)

Environment variables:

• MCP_HOST — bind address (default 0.0.0.0)
• MCP_PORT — MCP port (default 8083)

Architecture

The generated code (todo_service.mcp.rs) provides:

• TodoServiceMcpServer trait — one async method per RPC, taking serde_json::Value args and returning Result<Value, McpError>
• TodoServiceMcpHandler<T> — wraps any T: TodoServiceMcpServer and implements rmcp::ServerHandler (tools, prompts, resources)
• serve_todo_service_mcp(impl, config) — convenience function that creates the handler and starts the transport
• serve_todo_service_mcp_stdio(impl) — shortcut for stdio transport

Dependencies

Crate	Purpose
rmcp	MCP Rust SDK (ServerHandler, transports)
async-trait	Async trait support
serde_json	JSON serialization for MCP args/results
prost / prost-types	Protocol Buffers runtime
tonic	gRPC runtime
tonic-reflection	gRPC server reflection
tokio	Async runtime
axum	HTTP server (used by rmcp streamable-http)