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The 2026-07-28 stateless MCP specification (MCP 2.0) is the most significant change to the Model Context Protocol since it first launched, and it has reignited my interest in a protocol that had been eclipsed by Skills and by agent harnesses with terminal and curl access.

Simon Willison frames the stateless MCP spec (MCP 2.0) as the biggest change to the protocol since launch, and recounts how MCP — introduced by Anthropic in November 2024 and surging through 2025 — was later eclipsed by Skills and terminal-and-curl agent harnesses that did most of the same work more flexibly. ✦ AI generated

Simon Willison · Simon Willison's Weblog · 2026-07-31 · original ↗

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Tuesday was Stateless MCP day - the rollout of MCP 2.0, or the 2026-07-28 Model Context Protocol specification to use the more formal but less memorable name. This is the most significant change to the MCP spec since it first launched, and has also served to reignite my personal interest in the protocol. For background: MCP is the Model Context Protocol, which describes a standard way to expose new tools to LLM-powered agent frameworks. It was introduced by Anthropic back in November 2024, had a huge spike of interest through much of 2025, and then became somewhat eclipsed by Skills (another Anthropic invention) when it became apparent that an agent harness with access to a terminal and curl could do most of what MCP did in a more flexible way.

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▦ Anthropic ✳ MCP ✳ Skills

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Mechanism · 1

Legacy stateful MCP required two HTTP requests — an initialize handshake to obtain a Mcp-Session-Id followed by the actual tool call — while stateless MCP collapses this to a single request, which is much cleaner to implement from both client and server sides and a better fit for scalable web applications that need no server-side session state.Simon Willison · Simon Willison's Weblog · conf 60%

Evidence · 2

Giving an agent a shell environment with internet access is fraught with risk and requires a strong driving model, whereas MCP tools are easier to audit and control and are simple enough that smaller laptop models can drive them, and the stateless spec greatly cuts client and server implementation complexity.Simon Willison · Simon Willison's Weblog · conf 75%Even though MCP has its own prompt injection security problems, arbitrary shell and curl access in an open network environment is much harder to keep secure, and MCP makes it easier to reason about agent capabilities and failure modes — which is why I plan to lean into MCP when building sensitive LLM applications.Simon Willison · Simon Willison's Weblog · conf 75%

In practice · 2

I couldn't find a great CLI tool for interactively probing an MCP server, so I had Codex help build mcp-explorer — a stateless Python CLI that needs no installation and runs via uvx against any MCP endpoint.Simon Willison · Simon Willison's Weblog · conf 70%datasette-mcp adds a /-/mcp endpoint to any Datasette instance exposing three tools — list_databases(), get_database_schema(), and read-only execute_sql() — giving agents the ability to run SQL queries against a hosted Datasette instance, and it is a fourth attempt that finally felt releasable thanks to the stateless spec.Simon Willison · Simon Willison's Weblog · conf 70%