Prompting

Catch Claude Making Things Up: The Free Lie Detector Prompt

One copy-paste prompt that splits any Claude answer into single claims, makes each one show where it came from, opens the real sources to check they actually say it, and hands you a clean answer with only what checks out. The full prompt, how to use it, the study behind it, and the catch

Alex ChenAlex Chen@nocodealex · 50,000+ follow on Instagram
4min read
1prompts to copy
10numbered steps
6sections

AI answers sound sure of themselves even when a detail is wrong. A made-up number, a study that doesn't exist, a quote nobody said: it all reads the same as the true parts. This free prompt turns Claude into its own lie detector. It checks the answer line by line, makes every claim show where it came from, flags anything it can't prove, and opens the real sources to make sure they're legit.

Here's the full prompt, how to use it, the study behind it, and the catch.

Why you need it

Researchers at Carnegie Mellon (Cash and Oppenheimer, published in Memory & Cognition in 2025) tested ChatGPT, Gemini and Claude Sonnet and Haiku against people. The chatbots overestimated how well they did, and unlike people, they didn't adjust after doing badly. On a sketch-guessing game, Gemini got fewer than 1 of 20 right on average, then guessed it had gotten about 14. Confidence isn't proof, so make the answer show its proof.

What it does

  1. Splits the answer into single claims, one fact per line.
  2. Gives each claim a source (title, publisher, link) or marks it UNVERIFIED. It is told never to invent a source.
  3. With web search on, opens every source and tags each claim LEGIT, MISMATCH or NOT FOUND.
  4. Shows a table with the problem claims at the top.
  5. Rewrites a clean answer with only the claims that checked out, plus a short list of what it couldn't verify.
Free, for your emailGet the full setup steps + the copy-paste setup prompt

Free, for your email

Get the full setup steps + the copy-paste setup prompt

The rest of this guide (4 more sections, 1 copy-paste prompt) opens right here. The setup prompt, one paste into Claude that sets it all up, comes by email only. Use your real address.

Unlocks: The lie detector prompt · How to use it · The catch · Sources

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