MCP Protocol Conformance
Conformance test harness for MCP servers
JSON-RPC 2.0, OAuth 2.1 PKCE, tool schemas, capabilities, smoke roundtrip, annotation hygiene. Spec versions 2024-11-05, 2025-03-26, 2025-06-18.
What it solves
Nothing in the MCP ecosystem asks a server whether it actually speaks the protocol. It either works with the client you happened to test against, or it does not, and you find out from a user. This is the harness that answers the question before you publish.
How it works
It drives a server over stdio and checks it against the protocol rather than against your expectations, and it ships both as a command you run and as a TypeScript library you import. Inside the StudioMeyer factory it is the gate every other build passes before promotion, so before anything goes to npm, to a marketplace or into an upstream pull request, it has been through this harness first.
When to use it
Install it as a development dependency the day you start a server, not the day before you publish one. A conformance failure found early is a small fix, and the same failure found after a marketplace listing is a version bump plus an apology.
When not to use it
Conformance is about the protocol, not about your tools being useful, correct or safe. A server can pass every check here and still hand back nonsense. For the input side there is mcp-gauntlet, for signatures mcp-server-attestation, and for the interface contract over time mcp-covenant.
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Language
TypeScript
Updated
2026-08-21
Install
npx -y mcp-protocol-conformance