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

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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)

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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.

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Full changelog

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