fact-check

fact-check is a skill for Claude Code from coolTheWorld/evolution-skills. It costs 33 tokens per session (1,191 once invoked), scanned A, original, Apache-2.0.

A fact-checking workflow that separates checkable facts from conclusions and opinions, verifies the facts online, and examines whether the conclusion follows.

In plain words
What is it for?
Use it to break down claims, trace facts to original sources, assign evidence-based verdicts, and audit the reasoning connecting evidence to conclusions.
Why use it?
It helps determine which parts of a claim are supported, which are uncertain, and how much confidence the overall claim deserves.

Skill for Claude Code

Written for Claude Code: disable-model-invocation in frontmatter.

Part of the evolution plugin — 11 skills shipped together

Good fit Use it to break down claims, trace facts to original sources, assign evidence-based verdicts, and audit the reasoning connecting evidence to conclusions.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cooltheworld/evolution-skills/fact-check
Install

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.

Any agent
npx skills add coolTheWorld/evolution-skills --skill fact-check
Clone the repo
git clone --depth 1 https://github.com/coolTheWorld/evolution-skills

Made for: Claude Code.

Or install evolution, the plugin that ships this one along with the rest of its 11 skills.

Wrote 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.

agentmods badge for fact-check

README.md
[![agentmods](https://agentmods.dev/badge/skills/cooltheworld/evolution-skills/fact-check.svg)](https://agentmods.dev/skills/cooltheworld/evolution-skills/fact-check)
Your own site
<a href="https://agentmods.dev/skills/cooltheworld/evolution-skills/fact-check"><img src="https://agentmods.dev/badge/skills/cooltheworld/evolution-skills/fact-check.svg" alt="Measured on agentmods" height="20"></a>
Per session 33 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,191 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00033 $0.01191
Opus 5 $0.00016 $0.00596
Sonnet 5 $0.00007 $0.00238
Haiku 4.5 $0.00003 $0.00119

Measured 7d ago against content hash e134985461c2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

fact-check 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.

skills/fact-check/SKILL.md · 72 lines

How it starts

The opening of the file, as written. The whole thing — 72 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Humans and models both hallucinate, and the text in front of you may be either's. Doubt it by default: split the claim into what can be checked and what cannot, trace every fact to its primary source and give it a verdict, and audit the inference from those facts before granting the conclusion.

Write in the language the user writes in.

1. Decompose the claim

If the user gave no claim, or a bare topic with nothing to check, ask one question for the text itself and stop.

Split the claim into three bins:

  • Facts — statements the outside world can confirm or refute: numbers, events, quotes, attributions.
  • Conclusions — what the claim infers from those facts.
  • Value judgements — what it holds good, bad, or worth doing; no evidence settles these, so name them and set them aside.

A sentence usually mixes all three ("the study shows X, so we should Y") — cut at the seams rather than binning whole sentences. Rewrite each fact as one checkable proposition with its who, what, when and where. For a plan or proposal the facts are its premises and the conclusion is that the plan reaches its aim.

Done when every statement in the claim sits in exactly one bin and every fact is a single proposition specific enough to be found true or false.

2. Verify each fact

Check every fact with WebSearch and WebFetch, tracing it to its primary source. A page that repeats the number is a copy of the claim, not evidence for it; your own recollection is a claim to check, never a source. At the primary source read four things:

  • Source — who originally produced it, and whether they are in a position to know.
  • Sample — what was measured, on whom, how many, how selected.
  • Date — when it was measured, and whether it is still current.
  • Full context — what the source says around the quoted part; a true sentence lifted from its qualifications is the commonest way a fact goes wrong.

Tag each fact with exactly one verdict:

  1. Verified — the primary source says this, in this scope.
  2. Holds but must be narrowed — true for a smaller population, period, or definition than the claim states; write the narrowed form.
  3. Disputed — credible sources disagree; name who and on what.
  4. Insufficient evidence — no primary source found either way; record what you searched and what would settle it.
  5. Clearly wrong — the primary source contradicts it; write the correction.

Read the full file on GitHub · 72 lines

Changes

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.

  1. 7d ago First seen · 72 lines · 33 tokens per session scan A e134985461c2

Subscribe to this mod's changes

fact-check is a skill published in the GitHub repository coolTheWorld/evolution-skills (5 stars, last pushed 5d ago), licensed Apache-2.0. It adds 33 tokens to every session and 1,191 once invoked, about $0.0002 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 2026-08-31.

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