A fact-checking skill for Claude. Given any body of text, Corroborate extracts its checkable claims, lets you choose which to pursue, searches for independent sources, and reports each claim with a reliability verdict — surfacing exaggerations, errors, and unsupported assertions rather than rubber-stamping the text.
| Report | Input | Mode |
|---|---|---|
| ikea-sustainability.md | IKEA FY24 sustainability claims | List |
| finland-nato.md | Finland NATO accession facts | List |
| eiffel-tower-annotated.md | Eiffel Tower facts | Annotated |
| sp500-revenue.md | S&P 500 sector revenue table | List |
This is a work in progress, please note:
- Works as a skill and can be run from any Claude front end: Chat, Cowork, Code, and API.
- Connected MCP tools (Google Drive, Gmail) are checked first when the claim may reference your own material; web search handles everything else.
- The two-phase checkpoint design keeps search costs down — you choose which claims are worth pursuing before any searches run.
- A triage list of extracted claims, grouped and numbered, for you to choose from
- A findings list — claims grouped by verdict, ordered from most to least problematic
- Or an annotated version of the original text with inline footnote markers showing the verdict for each claim
Claims are assigned one of six verdicts, from most to least reliable:
- Strongly corroborated — confirmed by an official/original source, or multiple independent quality sources, with no discrepancy
- Corroborated — confirmed, but only by news/comment sources, or with a minor noted discrepancy
- Partially corroborated — the gist holds but a number, qualifier, or attribution is off
- Exaggerated — the underlying fact is real but overstated in scale, strength, or certainty
- Uncorroborated — no sources found (not the same as false)
- Contradicted — sources actively dispute the claim, or the discrepancy is severe enough to misrepresent reality
- You paste (or point to) the text you want checked
- Corroborate extracts the checkable claims and presents a numbered triage list
- You choose which claims to pursue — all, a range, or a category
- It searches for sources claim by claim, ranks them by quality, and checks for drift
- You choose list or annotated output, and the report is produced
The checkpoint after step 3 is intentional — it keeps the skill from burning searches on claims you don't care about.
Drop SKILL.md into your Claude skills directory:
| Environment | Skills directory |
|---|---|
| Claude Code | ~/.claude/skills/corroborate/SKILL.md |
| Claude Cowork | Via the Claude Desktop skills panel |
Then restart your Claude environment.
/corroborate
Then paste the text, or describe where to find it. Corroborate also triggers on natural language like "fact-check this", "can you verify these claims?", "is this true?", or "find sources for this report".
- A Claude environment that supports skills (Claude Code or Claude Cowork)
- At least one research tool available (web search, or connected MCP servers)
MIT — see LICENSE.