- The 2026-07-28 Model Context Protocol (MCP) specification introduces a stateless protocol core, transforming MCP from a bidirectional stateful protocol into a request/response stateless one for improved reliability and scalability.
- Every request is self-describing with optional discovery; methods and tool names travel in HTTP headers for routing and authorization.
- Multi Round-Trip Requests (MRTR) replace server-initiated bidirectional streams, enabling stateless interactions like user input requests mid-call.
- List responses now include cache hints (ttlMs, cacheScope) for better caching of tool catalogs and prompt lists.
- Authorization hardening includes RFC 9207 issuer validation, client metadata documents (CIMD) replacing Dynamic Client Registration (DCR), and client credentials bound to issuers.
- Tasks move out of experimental core into a formal extension; Roots, Sampling, Logging, and legacy HTTP+SSE transport are deprecated with a 12-month window.
- Updated TypeScript, Python, Go, C# SDKs are available with migration notes; Rust SDK supports the new spec in beta.