MCP specification 2025-11-25
The last revision built on the initialize handshake. Most clients in the field still speak it, so it is the baseline every MCP server needs to handle.
Status
Superseded: the versioning page names 2026-07-28 as the current version. [source]
How the version is agreed
In the initialize request, the client MUST send a protocol version it supports.
[source]
Clients seen speaking it
No tested client has used this revision in its latest test. That is an observation, not a claim that clients can't speak it.
Key changes
Allow servers to expose icons as additional metadata for tools, resources, resource templates, and prompts
[source]Added support for URL mode elicitation
[source]Add tool calling support to sampling via tools and toolChoice parameters
[source]Add support for OAuth Client ID Metadata Documents as a recommended client registration mechanism
[source]Add experimental support for tasks
[source]