Verifying Claims Skill for Claude

verifying-claims

Check that what a document *says* about code is true, by reading the document,

the code, and the tests together and reporting where they disagree.

What changed (v0.1 → v0.2)

v0.1 was a comment-DSL: you hand-wrote <!-- claim: ... --> next to prose and

a script checked the *comment* against the code. That had a fatal gap — the

comment and the prose were two artifacts stapled together, and only the comment

was checked, while humans read the prose. The prose could lie with a green run.

v0.2 drops the DSL. The reviewer is the agent: it reads the prose's *meaning*

directly and compares it to what the code does and what the tests assert. No

shadow copy, because the thing being checked is the thing the human reads.

(Existing tools already own the alternatives — Gherkin binds executable

scenarios, Lean's Verso transcludes facts into prose, TDD couples code to

tests. This fills the remaining slot: free-prose documentation, judged.)

Division of labor — read this first

This skill does NOT gate merges and is NOT a test framework.

• The test suite (TDD/CI) owns the behavioral contract: deterministic,

cheap, auditable, gated. A green check is something you can hold CI to.

• This skill owns the prose layer: does the documentation match reality?

That needs semantic judgment across artifacts, which is non-deterministic and

fallible — so it runs as a *triggered review* (before docs ship, on request,

as a sweep), not as a per-commit gate. "The agent said the docs match" is not

a guarantee you gate a merge on; it's a review you act on.

Tests are the anchor. The docs are correct when they agree with what the tests

assert about the code. So write/keep good tests first; this skill keeps the

prose pinned to them.

Procedure

• Identify the document(s) to check and the code + tests they describe.
• Gather consistent input: run `scripts/gather_context.py --doc DOC --src

SRC --tests TESTS`. It ast-parses source (no imports, no execution) and

bundles the document text, the public API surface, and the test inventory.

• Extract the claims the prose makes — every checkable assertion about the

code (signatures, behavior, return shapes, defaults, guarantees, examples).

Do this by reading; there are no claim markers.

• Judge each claim against the API surface and the tests:
• Does the code actually do what the prose says?
• Is the claim backed by a test, or merely asserted?
• Does it reference something that no longer exists?
• Report drift, ranked by severity, each finding citing the prose claim and

the contradicting reality (file/function). Use the verdicts below.

• Optionally fix: rewrite the prose to match reality, and/or flag claims

that need a test (an UNSUPPORTED claim is a missing test, not just a doc bug).

Verdicts

• PASS — the prose claim matches the code and is exercised by a test.
• FAIL — the code contradicts the claim (the doc is wrong, or the code

regressed and the doc caught it).

• UNSUPPORTED — the claim matches the current code but no test backs it, so

nothing protects it from future drift. Surface as a missing test.

• STALE — the claim refers to something removed or renamed.

Invoking

• "Check the README against the code before I publish it."
• "Does docs/api.md still match pkg/?"
• "Sweep the docs for drift after this refactor."

Run it at moments that matter — pre-publish, post-refactor, on a docs PR — not

on every commit. The deterministic gate is the test suite; this is the layer

tests can't reach.

Honest limits

• Non-deterministic and fallible: a review can miss drift or misjudge. Treat

output as a careful review, not a proof.

• Cost/latency: reading three artifacts and reasoning is expensive next to a

test run. Don't wire it where a cheap deterministic check belongs.

• It checks prose against code+tests; it does not verify the tests themselves

are correct. Garbage tests → confident-but-wrong PASS. TDD discipline upstream

still matters.

When NOT to use

• As a CI merge gate (use the test suite).
• To verify behavior (write a test).
• On prose with no factual claims about code (nothing to check).

Files

• scripts/gather_context.py — deterministic input bundler (doc + API surface +

test inventory), ast-only, no imports.

• references/drift-report-example.md — what a review report looks like.