MCP 2025-03-26
SUPERSEDED Confidence: High (1.00)MCP 2025-03-26 is a superseded revision of the Model Context Protocol specification, released 2025-03-26.
What is MCP specification revision 2025-03-26?
MCP 2025-03-26 is a superseded revision of the Model Context Protocol specification, released 2025-03-26.
Added the OAuth 2.1 authorization framework, replaced the original HTTP+SSE transport with Streamable HTTP, and added JSON-RPC batching and tool annotations.
What changed in MCP 2025-03-26?
- Comprehensive authorization framework based on OAuth 2.1
- Streamable HTTP transport replaces the previous HTTP+SSE transport
- JSON-RPC batching support
- Tool annotations describing tool behavior (read-only, destructive)
- Audio content type joins text and image
MCP 2025-03-26 introduced the Streamable HTTP transport that remote MCP servers still use today, replacing the original HTTP+SSE transport, and added the protocol's first comprehensive authorization framework, based on OAuth 2.1. It also added JSON-RPC batching (removed again in the following revision) and tool annotations for describing tool behavior.
How was this verified, and what are the sources?
Verified · method: spec-changelog
· confidence 1.00 (High).