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fact-checker — Claude Code subagent: verify claims and sources

A Claude subagent that pulls verifiable claims out of a text and rates how trustworthy the sources behind them are. Handy before you publish a draft or repeat someone's number.

Install into Claude Code · claude-code-templates All methods and platforms ↓ 
npx claude-code-templates@latest --agent deep-research-team/fact-checker
Open on GitHub

What fact-checker does

The subagent extracts specific claims: statistics, attributions, causal statements. Then it looks for supporting and contradicting evidence, compares them, and assigns a status from TRUE down to UNVERIFIABLE. Source credibility gets its own pass — domain type, methodology, signs of bias.

Under the hood is a Python engine class. It matches numeric claims by pattern, collects sources on both sides, and computes a confidence score between 0.0 and 1.0. WebSearch and WebFetch handle the lookups and page fetches; Read, Write and Edit cover files.

The source text is cut off, so the full verification routine isn't visible from it. No web access means no evidence gathering — worth checking your web tools are enabled before you rely on it.

What it helps with

  • break a draft into claims that can actually be checked
  • judge whether a given site or article deserves trust
  • trace a statistic back to its original source
  • catch a false claim before the piece goes out
  • verify a quote and who it is attributed to

Example prompts for the agent

  • fact-check this draft and flag the claims that don't hold up
  • assess how credible this source is
  • find the original source for this statistic

How to install fact-checker

1claude-code-templates

npx claude-code-templates@latest --agent deep-research-team/fact-checker

2Manually: put the files in place

.claude/agents/fact-checker.md

For all projects use ~/.claude/agents/. Claude delegates by the description field or an @-mention

Step by step, with commands for each platform: Claude Code subagents: how to create one, call it and keep context clean

Questions about fact-checker

How do I install fact-checker in Claude?

Use the templates CLI: npx claude-code-templates@latest --agent deep-research-team/fact-checker. The subagent file lands at .claude/agents/fact-checker.md.

What does fact-checker do?

It verifies claims in a text, searches for supporting and contradicting evidence, assesses source credibility, and assigns each claim a verification status.

What tools does the subagent need?

Its description lists Read, Write, Edit, WebSearch and WebFetch. Without web search access, checking outside sources won't work.

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