05-fact-check

Fact-check

Verifies the factual claims inside a target text and rewrites it grounded in evidence. The skill extracts each verifiable claim, runs a cheapest-first verification cascade, and emits a rewritten answer where every confirmed claim carries a footnote citation and every unconfirmed claim is explicitly hedged. When sources disagree, both are reported rather than one being silently chosen.

Available actions

#	Action	Role	Input
01	identify-claims	Extract verifiable factual claims from the text, classify each, drop opinion	target text
02	verify	Run the verification cascade per claim, produce a verdict and sources	claim list from 01
03	report	Rewrite the text with footnote citations, hedge unverified, surface conflicts	verdict list from 02

Default flow

Sequential skill: 01 → 02 → 03. No skipping. The router materializes the three actions as a task list on entry and closes each task only when its ## Test passes.

Transversal rules

• Never alter the meaning of a claim while verifying it - verify what was stated, not a charitable reinterpretation.
• The verification cascade is cheapest-first and short-circuits: stop at the first tier that resolves a claim. See @references/verification-cascade.md.
• A web lookup is the last resort, never the first. Reach it only when project memory and codebase inspection both fail to resolve a claim.
• Claim categories come from the locked set in @references/claim-categories.md. Opinion, preference, and trivially-known statements are not claims and are skipped.
• When two sources disagree, report both with their origin - never silently pick one.
• An unverified claim is never deleted and never asserted as fact: it is kept and marked (unverified - no source found).
• Caching a verified fact is opt-in: propose it with a recommendation, never cache silently. The skill itself stores nothing - on approval it restates the fact for the user's own memory tooling. Persistence is out of scope.
• The final report is reader-facing prose - the corrected text, ## Sources, and ## Unverified claims, nothing else. Internal mechanics never appear in the output: no cascade or tier trace (Cascade:, tier 1/2/3, miss, resolved), no category labels, no raw verdict words. State conclusions, not the process. Action 03 holds the exhaustive forbidden list.
• The report is rendered in plain prose and is never restyled by an active session output mode (terse, caveman, condensed). The skill's output format is fixed by action 03 alone.

References

• @references/claim-categories.md - locked taxonomy of verifiable claim categories with definition and example.
• @references/verification-cascade.md - the three-tier cascade, short-circuit rule, web-cost guardrail.

Assets

• @assets/report-template.md - rewritten-answer skeleton with the ## Sources footnote block.

External data

• None.