Truth Serum: every claim checked at its source before you publish
Truth Serum is a skill for Claude that fact-checks a draft or a live page, including text an AI wrote. It lists every checkable claim (prices, menu labels, versions, statistics, quotes), looks for the exact string on the primary source, in the page's own language, and gives each a verdict and a ready-to-paste correction.
One of the 14 skills in the pack
Ask it in your own words
- "Check this article's facts before I publish."
- "An AI wrote this draft. Make sure the menu names and versions are real."
- "Does the French version say the same as the English one?"
- "i think theres a wrong number somewhere on my pricing page, no idea where"
What happens next
- It lists the claims and ranks them. extract_claims.py finds the sentences with a number, a label or a version, and Claude reads the rest. What a reader pays for or follows step by step comes first.
- It checks each one at the source. It opens the page of whoever creates the fact and searches the literal string in the raw page, never a summary.
- It gives a verdict and a patch. Each wrong sentence leaves with its correction, and site_grep.py finds the other pages that repeat it.
What you get back
- A claims ledger: each claim with its risk, source URL, string found and one of five verdicts
- A patch list: old sentence, new sentence, why, where else to fix it
- The questions only you can answer, and the places where the page contradicts itself
- A publish gate, PASS or BLOCKED, and the next re-check date
Run on this very site
The claims of the home page, listed before each one was checked.
candidate claims: 47 rows [...] rows per type [...]: absolute 11, comparison 9, date 4, price 15, statistic 9, version 5
C004 | high | statistic,absolute | statistic: 4.2k | absolute: Zero | Zero to 4.2k Google clicks in three months. | 1 (h1)
Possible internal conflicts: None found among 9 price rows (rows carrying a currency amount).The figures were checked against the Search Console screens they come from, and the price against the payment page: 25 euros, tax included.
What it will not do
- It reads pages as a raw fetch does: one location, no JavaScript. Pages with region prices or bot protection are reported as unreadable, never "not found".
- It refuses to mark a claim verified without checking, to back-date a "checked on" line or to add a "fact-checked" badge nobody earned.
- It promises no error-free page, and legal or medical statements still need a qualified reviewer.
What it needs
Claude Code or the Claude apps, with code execution (Python 3.9 or later) for the three scripts. Where they cannot reach the web, there is a manual route: Claude locates the source page and you paste the paragraph or a screenshot.
How to install a skill in Claude
Guides
Where it hands over
- Best Before: It takes the dated facts and re-checks them on a schedule, across the whole site.
- Fair Fight: For a comparison page, its audit mode rebuilds the facts table from the live page.
Questions about this skill
Which languages does it handle?
It checks each label on the source page of its own language, and never carries an English label into a translation. The claim extractor knows the wording of six languages (English, French, Spanish, German, Italian, Portuguese) and finds numbers, prices and versions in any.
Can it check a page that is not mine?
Yes. You get the ledger and the wrong or unsupported statements, with suggested wording for the author.
It comes with the 13 others.
One pack, one payment: the 14 skills, their scripts, templates and reference notes.
One payment, no subscription. In your inbox within a minute, as a rule.