MCP Specification 2026-07-28

The July 28 MCP revision changes how AI applications communicate with tool servers: each request carries the information needed to handle it without a persistent protocol session. A service can distribute requests across server instances without maintaining shared session state.

Applications can still remember ongoing work by returning an explicit handle that subsequent tool calls carry back. When a tool needs user input, the server can return a request for that input and let the client retry with the answer. This moves coordination into explicit messages, reducing reliance on continuously open connections while preserving multi-step interactions.

“Across our Tier 1 SDKs, we’re seeing close to half-a-billion downloads a month, with both TypeScript and Python SDKs crossing the 1 billion total downloads threshold.”

ClaudeDevs

“The highlight of this release is a stateless protocol core - MCP is transforming from a bidirectional stateful protocol into a request/response stateless protocol.”

ClaudeDevs

“With the new spec version, we’ve officially retired the initialize / initialized exchange along with the Mcp-Session-Id header (refer to SEP-2575 , SEP-2567 ). Each request now travels on its own, carrying its protocol version, client identity, and client capabilities in _meta .”

ClaudeDevs

“Dropping the protocol-level session doesn’t force your application to be stateless. If your server needs to carry state across calls, mint an explicit handle from a tool and have the model pass it back as an argument. We found this works better than session state hidden in the transport - the model can see the handle and thread it between tools.”

ClaudeDevs

“Dynamic Client Registration itself is now formally deprecated in favor of CIMD. DCR continues to work for backward compatibility, but will be removed in a future version of the MCP spec.”

ClaudeDevs