MCP's 2026-07-28 spec drops the session handshake for a single HTTP POST
The 2026-07-28 Model Context Protocol spec replaces the initialize-then-call handshake with one HTTP POST carrying MCP-Protocol-Version, Mcp-Method, and Mcp-Name headers. Servers stop tracking session IDs and stop pinning a session to one backend machine, which turns an MCP endpoint into an ordinary scalable web endpoint. Simon Willison built three clients on the new spec in a week — mcp-explorer, datasette-mcp, and an alpha llm-mcp-client plugin — and mcp-explorer probes any server with no install via uvx.
Source: simonwillison.net ↗
It's also a better fit for building scalable web applications, since now you don't need to maintain server-side state to keep track of those session IDs, or worry about routing the same session to the same backend machine.
Why this matters
- → Eliminates session tracking burden; MCP endpoints now scale like ordinary web services.
- → Dramatically simpler to implement both clients and servers.
- → Smaller models can now drive MCP tools safely, without needing shell access.