Documentation Index

Fetch the complete documentation index at: https://modelcontextprotocol.io/llms.txt Use this file to discover all available pages before exploring further.

Key Changes

This document lists changes made to the Model Context Protocol (MCP) specification since the previous revision, 2024-11-05.

Major changes

1. Added a comprehensive authorization framework based on OAuth 2.1 (PR #133)
2. Replaced the previous HTTP+SSE transport with a more flexible Streamable HTTP transport (PR #206)
3. Added support for JSON-RPC batching (PR #228)
4. Added comprehensive tool annotations for better describing tool behavior, like whether it is read-only or destructive (PR #185)

Other schema changes

• Added message field to ProgressNotification to provide descriptive status updates
• Added support for audio data, joining the existing text and image content types
• Added completions capability to explicitly indicate support for argument autocompletion suggestions

See the updated schema for more details.

Full changelog

For a complete list of all changes that have been made since the last protocol revision, see GitHub.

Last updated Oct 08, 2026