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:

(Sink, Stream) or a combined Sink + Stream
(AsyncRead, AsyncWrite) or a combined AsyncRead + AsyncWrite
A Worker implementation
A Transport implementation directly

License