原文
This document lists changes made to the Model Context Protocol (MCP) specification since the previous revision, 2025-03-26.
Major changes
- Remove support for JSON-RPC batching (PR #416)
- Add support for structured tool output (PR #371)
- Classify MCP servers as OAuth Resource Servers, adding protected resource metadata to discover the corresponding Authorization server. (PR #338)
- Require MCP clients to implement Resource Indicators as described in RFC 8707 to prevent malicious servers from obtaining access tokens. (PR #734)
- Clarify security considerations and best practices in the authorization spec and in a new security best practices page.
- Add support for elicitation, enabling servers to request additional information from users during interactions. (PR #382)
- Add support for resource links in tool call results. (PR #603)
- Require negotiated protocol version to be specified
via
MCP-Protocol-Versionheader in subsequent requests when using HTTP (PR #548). - Change SHOULD to MUST in Lifecycle Operation
Other schema changes
- Add
_metafield to additional interface types (PR #710), and specify proper usage. - Add
contextfield toCompletionRequest, providing for completion requests to include previously-resolved variables (PR #598). - Add
titlefield for human-friendly display names, so thatnamecan be used as a programmatic identifier (PR #663)
Full changelog
For a complete list of all changes that have been made since the last protocol revision, see GitHub.