factchk
Fact-checks assertions against external sources to prevent relying on faulty intuition or unverified claims.
Install
mkdir -p .claude/skills/factchk && curl -L -o skill.zip "https://agentskills.codes/api/skills/download/17572" && unzip -o skill.zip -d .claude/skills/factchk && rm skill.zipInstalls to .claude/skills/factchk
Activation
This is the description your AI agent reads to decide when to run this skill — the better it matches your request, the more reliably it fires.
Verify reality-grounded claims against external sources in both directions before they ship — could the 'absurd' be real, could the 'obvious' be false or long-established? Use whenever an artifact, or the sentence you are about to write, asserts something as plausible, realistic, absurd, novel, or impossible from intuition rather than a checked source; before relying on a factual claim in prose, a design rationale, a research claim, or a plan. Fires on metacognitive doubt — when you can't actually know, verify instead of trusting the feeling. Scans read-only, then fixes the clear errors or flags the judgment calls; leaves deliberate fiction alone.Key capabilities
- →Scan for reality-grounded assertions in text
- →Verify claims against external sources
- →Identify if 'absurd' claims could be real
- →Determine if 'obvious' claims are false or established
- →Correct mechanically clear errors with cited sources
- →Flag judgment calls or contested claims for review
How it works
The skill scans text for reality-grounded assertions, then verifies each against external sources in both directions. It corrects clear errors with citations or flags judgment calls for human review.
Inputs & outputs
When to use factchk
- →Checking technical documentation for accuracy
- →Verifying claims in project specs
- →Ensuring data integrity in reports
About this skill
Check what's asserted as real against reality — in both directions — before it ships.
Goal
The author's "plausible / absurd / novel" is the least reliable line in any artifact. Human priors fail both ways — they exclude the real (desert frogs exist) and normalize the impossible (weightless crates). factchk scans claims presented as reality-grounded, verifies each against external sources in both directions, and fixes or flags. Its scope is a claim about the world — whether what's asserted as real is real — not the soundness of a validation or the survival of a whole plan.
Workflow
- Scan for reality-grounded assertions — anything leaning on "this is plausible / realistic / absurd / novel / impossible because X," including the claim you are about to write, not only those already on the page.
- Verify each against external sources (web search, open references) in both directions: could the "absurd" be real? could the "obvious" or "novel" be false or long-established? If you cannot reach a source, flag — never assert from intuition.
- Fix or flag: a mechanically-clear error (a wrong date, a misattributed source, a falsified number) → correct it with a cited source; a judgment call (a contested or interpretive claim) → surface it, don't silently rewrite.
- Report each claim, its verdict, the source, and — for a failed claim — which direction it failed.
Rules
- Target claims asserted as reality-grounded, never deliberate fiction ("in our world, boxes float" is a declared choice). When it is unclear whether a claim is an in-world choice or a real-world assertion, flag, don't fix — the hardest call in the skill.
- Flagging only the unrealistic catches half the errors.
- The trigger is metacognition, not knowledge: you can't know every domain, so the moment you are about to assert a checkable fact from a feeling, verify it instead of trusting the feeling.
- A pass that finds nothing changes nothing.
Verification
Before finishing: every verdict traces to a citable external source, not a reworded prior intuition — and the report reads as fixes-vs-flags, not restated intuitions.
When not to use it
- →When claims are deliberate fiction
- →When the goal is to silently rewrite contested claims
- →When only flagging unrealistic claims
Limitations
- →Does not fix deliberate fiction
- →Requires external sources for verification
- →Flags judgment calls instead of rewriting them
How it compares
This skill actively verifies claims against external sources to confirm or refute them, rather than relying on intuition or simply accepting stated facts.
Compared to similar skills
factchk side by side with the closest alternatives in the catalog.
| Skill | Installs | Updated | Safety | Difficulty |
|---|---|---|---|---|
| factchk (this skill) | 0 | 21d | No flags | Intermediate |
| citation-management | 23 | 7mo | Review | Beginner |
| microsoft-docs | 10 | 4mo | Review | Beginner |
| peer-review | 11 | 7mo | Review | Advanced |
Try saying
Example prompts that trigger this skill in your AI assistant.
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