Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add SkillMedev/skills --skill fact-checkergit clone --depth 1 https://github.com/SkillMedev/skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/skillmedev/skills/fact-checker)<a href="https://agentmods.dev/skills/skillmedev/skills/fact-checker"><img src="https://agentmods.dev/badge/skills/skillmedev/skills/fact-checker/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/skillmedev/skills/fact-checker"><img src="https://agentmods.dev/badge/skills/skillmedev/skills/fact-checker.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00126 | $0.01209 |
| Opus 5 | $0.00063 | $0.00605 |
| Sonnet 5 | $0.00025 | $0.00242 |
| Haiku 4.5 | $0.00013 | $0.00121 |
Grade A, and why
Fact Checker scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
1 near-identical copy found in the catalogue:
- Fact Checker — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Fact Checker
Treat every claim as unproven until corroborated. The job is calibrated truth, not a verdict for its own sake - and the costly failure this skill prevents is the confident verdict built on correlated sources: three outlets repeating one wire story feels like consensus and is actually a single point of failure. "I can't verify this" is a valid, honest answer; a fabricated citation is never acceptable.
Inputs to collect
Gather these before checking anything. If the user cannot supply one, use the default and label the assumption.
- The exact claim, verbatim. Paraphrase later; anchor on the original wording first.
- Where it appeared and what is at stake (publishing it, acting on it, arguing against it). Stakes set the sourcing bar - anything being published gets the full two-independent-primary-sources standard.
- Depth and deadline. Default: full check.
- Any sources the user already has. Treat these as leads, not evidence, until appraised.
Operating procedure
Follow in order - the verdict scale is meaningless if the claim was never isolated.
- Isolate the claim. Restate it as one or more precise, checkable propositions. Split vague or compound claims into parts and give each part its own verdict. Separate the factual core from interpretation or spin; check the core.
- Gather sources. Prefer primary sources - official data, original papers, direct statements - over summaries of them. Find at least two independent ones per proposition before any strong verdict.
- Check independence. Three outlets citing the same wire story is one source, not three. Same press release, same underlying dataset, same original interview: one source. A company or person making a claim about itself is one interested source, whatever its reach.
- Weigh evidence. Note recency, authority, method, and conflicts of interest. Weigh sources; never average them - one rigorous primary source outweighs five repetitions of a rumor.
- Assign verdict and confidence. Use the scale below, state confidence (high / moderate / low), and state what specific evidence would change the verdict.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 66 lines · 126 tokens per session scan A c1c2803c68f9
Fact Checker is a skill published in the GitHub repository SkillMedev/skills (12 stars, last pushed 2mo ago), licensed MIT. It adds 126 tokens to every session and 1,209 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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