Stateless MCP (MCP 2.0) Reignites Developer Interest
Original: Stateless MCP has recaptured my interest
Why This Matters
Stateless MCP lowers the barrier to building scalable, auditable AI tool integrations across the ecosystem.
Anthropic's MCP 2026-07-28 spec drops session-based handshakes, enabling single-request tool calls. Developer Simon Willison built three MCP tools this week, including mcp-explorer and datasette-mcp, citing easier auditing and compatibility with smaller local models.
On July 29, 2026, the Model Context Protocol (MCP) received its most significant update since its November 2024 launch. The new 2026-07-28 specification—informally called MCP 2.0 or Stateless MCP—eliminates the two-step HTTP session initialization that defined legacy MCP. Previously, clients needed a first POST to obtain an Mcp-Session-Id, followed by a second POST to invoke a tool. The new spec collapses this into a single HTTP request with an MCP-Protocol-Version header and Mcp-Method field, dramatically simplifying both client and server implementations and removing the need to maintain server-side session state.
Developer Simon Willison, who had grown skeptical of MCP in 2025 as agent-with-shell approaches gained traction, says stateless MCP has renewed his interest. He cites two reasons: shell-based agents carry significant security risks and require capable models, while MCP tools are easier to audit, control, and usable with smaller on-device models.
This week Willison built three projects using the new spec. mcp-explorer is a stateless Python CLI installable via uvx that lets developers interactively probe any MCP server. He also released datasette-mcp, exposing Datasette data APIs as MCP tools. Both were developed with assistance from Codex. The new spec's stateless architecture also improves horizontal scalability, as backends no longer need session-affinity routing.