modelcontextprotocol/rust-sdk

An official Rust Model Context Protocol SDK implementation with tokio async runtime.
> Migrating to 3.x? See the migration guide for breaking changes and upgrade instructions.
This repository contains the following crates:
rmcp: The core crate providing the RMCP protocol implementation - see rmcp
rmcp-macros: A procedural macro crate for generating RMCP tool implementations - see rmcp-macros
This SDK implements the stable MCP 2026-07-28 specification while
remaining fully compatible with the 2025-11-25 release and earlier
versions. Features introduced in 2026-07-28 — server discovery & negotiation,
transport-neutral subscriptions, long-running tasks, response caching,
multi-round-trip requests, and standard HTTP routing headers — are documented
below. For the full MCP specification, see
modelcontextprotocol.io.
## Table of Contents
Usage
Tools
Resources
Prompts
Sampling
Elicitation
Roots
Logging
Completions
Notifications
Subscriptions
Multi-Round-Trip Requests
Tasks
Caching
Standard HTTP Headers
Stateless Streamable HTTP
Transports
Pagination
Capability & Protocol Version Negotiation
JSON Schema 2020-12
Examples
OAuth Support
Related Resources
Related Projects
Development
## Usage
### Import the crate
Add the latest published version with cargo:
sh
cargo add rmcp --features server
Or use the dev channel:
sh
cargo add rmcp --features server --git https://github.com/modelcontextprotocol/rust-sdk --branch main
### Third Dependencies
Basic dependencies:
tokio
serde
Json Schema generation (version 2020-12):
schemars
### Build a Client
Start a client
rust, ignore
use rmcp::{ServiceExt, transport::{TokioChildProcess, ConfigureCommandExt}};
use tokio::process::Command;
#[tokio::main]
async fn main() -> Result > {
let client = ().serve(TokioChildProcess::new(Command::new("npx").configure(|cmd| {
cmd.arg("-y").arg("@modelcontextprotocol/server-everything");
}))?).await?;
Ok(())
### Client lifecycle modes
serve() uses the legacy MCP lifecycle: the client sends initialize, receives
the negotiated server information, and then sends notifications/initialized.
Use ClientServiceExt::servewithlifecycle to
select another lifecycle explicitly:
rust, ignore
use rmcp::{ClientLifecycleMode, ClientServiceExt, ProtocolVersion, model::ClientConfig};
// Start directly with server/discover and include client metadata on every request.
let client = ClientConfig::default()
.servewithlifecycle(
transport,
ClientLifecycleMode::Discover {
preferredversions: vec![ProtocolVersion::V20260728],
},
.await?;
// Or probe the discover lifecycle and fall back when a legacy server reports
// that server/discover is not implemented or does not respond within 10 seconds.
let client = ClientConfig::default()
.servewithlifecycle(
transport,
ClientLifecycleMode::Auto {
preferredversions: vec![ProtocolVersion::V20260728],
legacyversion: Some(ProtocolVersion::V20251125),
},
.await?;
ClientLifecycleMode::Initialize is equivalent to the existing serve() behavior.
Discover startup does not send notifications/initialized; discovery completes
startup, and each subsequent request carries its protocol version, client
information, and capabilities in meta.
### Build a Server
Build a transport
rust, ignore
use tokio::io::{stdin, stdout};