wtf is mcp-spec-check?

mcp-spec-check is a command line tool that checks whether a live MCP server is ready for the 2026-07-28 update to the Model Context Protocol spec, the largest revision since the protocol launched. You run it against any server URL and it tells you, in about 30 seconds, whether that server has moved to the new stateless way of handling connections or is still relying on features the new spec removes, like the old handshake and session identifiers. The tool works as a black box: it sends read only probe requests to your server's public endpoint and does not need access to your source code. Nothing is installed on the server and nothing is stored beyond the report you receive. The main verdict, ready or not ready, is decided by three required checks: whether the server supports the new discovery method, whether it includes the new routing headers on every request, and whether it can run without being pinned to a single session, which matters for servers sitting behind load balancers. Five additional checks are optional and only shown as warnings, so they cannot on their own cause a server to be marked not ready. If a check gives an unclear answer, the tool marks it inconclusive rather than guessing. The author ran the tool against nearly all 7,850 servers listed in the official MCP registry in mid July 2026 and found that fewer than one in ten were ready, with the full results published in the repository's docs folder. To make sure the checks themselves are trustworthy, the project runs two reference servers, one on the old spec and one on the new release candidate, in continuous integration on every build, and compares its verdicts against the official conformance test suite as well. You can run it with npx and no installation, get output as plain text or JSON for scripts, pass authentication headers or bearer tokens for private servers, and set a custom timeout. Exit codes are designed for use in CI pipelines: zero means ready, one means at least one check failed, and two means the tool could not test the server at all. The project is written in TypeScript, has zero runtime dependencies, and is released under the MIT License.