rust-sdk/crates/rmcp

rmcp

The official Rust SDK for the Model Context Protocol. Build MCP servers that expose tools, resources, and prompts to AI assistants — or build clients that connect to them.

For getting started, usage guides, and full MCP feature documentation (resources, prompts, sampling, roots, logging, completions, subscriptions, etc.), see the main README.

Feature Flags

Feature	Description	Default
server	Server functionality and the tool system	✅
client	Client functionality
macros	#[tool] / #[prompt] macros (re-exports rmcp-macros)	✅
schemars	JSON Schema generation for tool definitions
auth	OAuth 2.0 authentication support
elicitation	Elicitation support

Transport features

Feature	Description
transport-io	Server-side stdio transport
transport-child-process	Client-side stdio transport (spawns a child process)
transport-async-rw	Generic async read/write transport
transport-streamable-http-client	Streamable HTTP client (transport-agnostic)
transport-streamable-http-client-reqwest	Streamable HTTP client with default reqwest backend
transport-streamable-http-server	Streamable HTTP server transport

TLS backend options (for HTTP transports)

Feature	Description
reqwest	Uses rustls — pure Rust TLS (recommended default)
reqwest-native-tls	Uses platform-native TLS (OpenSSL / Secure Transport / SChannel)
reqwest-tls-no-provider	Uses rustls without a default crypto provider (bring your own)

Transports

The transport layer is pluggable. Two built-in pairs cover the most common cases:

	Client	Server
stdio	TokioChildProcess	stdio
Streamable HTTP	StreamableHttpClientTransport	StreamableHttpService

Any type that implements the Transport trait can be used. The IntoTransport helper trait provides automatic conversions from:

1. (Sink, Stream) or a combined Sink + Stream
2. (AsyncRead, AsyncWrite) or a combined AsyncRead + AsyncWrite
3. A Worker implementation
4. A Transport implementation directly

License

This project is licensed under the terms specified in the repository's LICENSE file.