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Key Changes changedspecification/2025-11-25/changelog

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11# Key Changes
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33This document lists changes made to the Model Context Protocol (MCP) specification since
4the previous revision, [2025-06-18](/specification/2025-06-18).
4the previous revision, [2025-06-18](/specification/2025-06-18.md).
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66## Major changes
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10103. Enhance authorization flows with incremental scope consent via `WWW-Authenticate` ([SEP-835](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/835))
11114. Provide guidance on tool names ([SEP-986](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1603))
12125. Update `ElicitResult` and `EnumSchema` to use a more standards-based approach and support titled, untitled, single-select, and multi-select enums ([SEP-1330](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1330)).
136. Added support for [URL mode elicitation](/specification/2025-11-25/client/elicitation#url-elicitation-requests) ([SEP-1036](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/887))
136. Added support for [URL mode elicitation](/specification/2025-11-25/client/elicitation.md#url-elicitation-requests) ([SEP-1036](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/887))
14147. Add tool calling support to sampling via `tools` and `toolChoice` parameters ([SEP-1577](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1577))
15158. Add support for OAuth Client ID Metadata Documents as a recommended client registration mechanism ([SEP-991](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/991), PR [#1296](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1296))
169. Add experimental support for [tasks](/specification/2025-11-25/basic/utilities/tasks) to enable tracking durable requests with polling and deferred result retrieval ([SEP-1686](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1686)).
169. Add experimental support for [tasks](/specification/2025-11-25/basic/utilities/tasks.md) to enable tracking durable requests with polling and deferred result retrieval ([SEP-1686](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1686)).
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1818## Minor changes
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20201. Clarify that servers using stdio transport may use stderr for all types of logging, not just error messages (PR [#670](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/670)).
21212. Add optional `description` field to `Implementation` interface to align with MCP registry server.json format and provide human-readable context during initialization.
22223. Clarify that servers must respond with HTTP 403 Forbidden for invalid Origin headers in Streamable HTTP transport. (PR [#1439](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1439))
234. Updated the [Security Best Practices guidance](https://modelcontextprotocol.io/specification/draft/basic/security_best_practices).
234. Updated the [Security Best Practices guidance](https://modelcontextprotocol.io/specification/draft/basic/security_best_practices.md).
24245. Clarify that input validation errors should be returned as Tool Execution Errors rather than Protocol Errors to enable model self-correction ([SEP-1303](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1303)).
25256. Support polling SSE streams by allowing servers to disconnect at will ([SEP-1699](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1699)).
26267. Clarify SEP-1699: GET streams support polling, resumption always via GET regardless of stream origin, event IDs should encode stream identity, disconnection includes server-initiated closure (Issue [#1847](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1847)).
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