MCP spec 2025-03-26
MCP revision 2025-03-26 adds an OAuth 2.1 authorization framework, replaces HTTP+SSE with Streamable HTTP, and adds batching and tool annotations.
Makes remote, authenticated MCP servers practical with OAuth 2.1-based authorization, Streamable HTTP transport, JSON-RPC batching (later removed in 2025-06-18), tool annotations (read-only vs destructive), audio content and progress messages.
- Date
- Wednesday, 26 March 2025
- Lab
- Anthropic
- Kind
- infra
- Access
- open standard
Spec revisions are identified by a date string, and it is treated here as the release date. Later revisions are 2025-06-18 (structured output, elicitation, OAuth resource servers), 2025-11-25 (tasks, client ID metadata documents) and 2026-07-28 (stateless core).
Sources
This record was checked against its sources on 6 October 2026. How we check