ironmcp

The hardening & conformance standard for MCP servers. Dedicated, hardened, conformant MCP tooling on every platform — so nobody hand-rolls JSON-RPC again.

ironmcp is a policy layer for Model Context Protocol servers. It ships no tools — it constrains how your tools behave. The Python kit targets mcp>=2.

The problem it fixes

Most MCP SDKs silently drop any argument a tool doesn't declare, before the tool runs — no error, no signal. One added letter (project → projects) yields a genuine answer to a question nobody asked, with no way for the caller to learn their constraint was ignored. ironmcp refuses the unknown argument instead, and advertises that it does.

Quick start

from ironmcp import strict_server

app = strict_server(name="my-server", version="1.0.0")

@app.tool()
async def search(query: str, limit: int = 20) -> str:
    ...

Now search(query="x", projekt="y") comes back as an error result ("unknown argument(s): projekt … Nothing was executed"), instead of silently running with projekt dropped. The advertised schema carries additionalProperties: false, so agents are told the truth — advertisement == runtime. A tool that sets additionalProperties: true opts out and accepts arbitrary keys.

Conformance — the guarantee is provable

from ironmcp import aassert_enforces_v2, run_corpus

await aassert_enforces_v2(app)                         # every tool: advertisement == runtime
results = await run_corpus(app, "conformance/cases")   # the language-neutral corpus
assert all(r.passed for r in results)

The behavioural contract lives in spec/, executable as conformance/ — a JSON corpus owned by no language. A kit in any language conforms when a server built with its strict layer passes the same cases. That is what makes "the same guarantee everywhere" provable rather than claimed.

Also included

• health_payload(name, version) / code_sha() — agent-interrogable liveness (an agent learns what a server is and whether it is current without asking a human).
• make_bearer_asgi(app, expected_token=...) — fail-closed bearer auth (401 + WWW-Authenticate) to wrap app.streamable_http_app().

API

from ironmcp import — strict_server, StrictArgsMiddleware, assert_enforces_v2, aassert_enforces_v2, run_corpus, Result, health_payload, code_sha, make_bearer_asgi.

See examples/demo.py for a runnable server that proves the guarantee end to end.

License

Apache-2.0. By Srclight.