MCP Rust SDK

license

Apache-2.0(OSI

source

public(the crate, its features and its examples)

self-host

yes(a library you build against)

core features withheld

no — nothing withheld from the published tree

Open source under the Model Context Protocol project's dual transition licence: Apache-2.0 for new contributions, MIT retained where authors have not consented to relicensing. GitHub's classifier reports NOASSERTION over it, which is a fact about the file's shape rather than the grant, and the body is cited.

• https://api.github.com/repos/modelcontextprotocol/rust-sdk recorded 2026-09-17

  Repository metadata: 3,935 stars, not archived, not a fork, last pushed 2026-09-15, description "The official Rust SDK for the Model Context Protocol".

• https://raw.githubusercontent.com/modelcontextprotocol/rust-sdk/main/LICENSE recorded 2026-09-17

  The LICENSE body, read rather than the classifier's label. It opens "The MCP project is undergoing a licensing transition from the MIT License to the Apache License, Version 2.0", licensing new contributions Apache-2.0, documentation CC-BY-4.0, and retaining MIT for contributions whose authors have not consented to relicensing. That transition preamble is what GitHub's classifier cannot match, and it is why the API reports NOASSERTION.

Adoption is measured through crates.io downloads for `rmcp`. That figure is a trailing 90-day count rather than a monthly one, so it is converted to a monthly rate on the assumption of a roughly even pace across the window.

• https://crates.io/api/v1/crates/rmcp recorded 2026-09-17

  The crates.io API record for `rmcp`: 27,118,854 downloads all-time and 14,002,418 recent_downloads, which crates.io defines as the trailing 90 days. Latest stable 3.4.0, updated 2026-09-15.

This SDK matches the official Go SDK's coverage of the Model Context Protocol: both roles, every primitive and the optional features, each tied to the 2026-07-28 specification. It ships stdio and Streamable HTTP but deliberately not the legacy two-endpoint HTTP+SSE transport, which the current specification does not require.

• https://raw.githubusercontent.com/modelcontextprotocol/rust-sdk/main/README.md recorded 2026-09-17

  The README: "This SDK implements the stable MCP 2026-07-28 specification while remaining fully compatible with the 2025-11-25 release and earlier versions." Tools, Resources and Prompts each have a section with a 2026-07-28 spec link, as do Sampling, Elicitation and Roots. The transport table lists stdio, child process, Streamable HTTP server and client, and in-process; on SSE it states "There is no separate 'SSE transport' to configure" and that the 2024-11-05 HTTP+SSE transport is "a deliberate non-goal".