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How to Fact-Check an AI Answer

Fact-checking an AI answer takes three habits: ask for sources and actually open them, re-run the one or two lookups the answer stands on, and keep a receipt of what the AI actually fetched. Most wrong answers fail one of those checks in under a minute. This page walks through them in plain language, no technical background needed.

See what a checkable lookup looks like: the live demo runs one real call and hands you a receipt for it, the same kind of record described below.

Updated October 20, 2026.

Quick checks you can do in a minute

Spotting made-up sources

The most dangerous AI errors wear a lab coat: a study that does not exist, a quote nobody said, a link that leads nowhere or to a page about something else. The tells are consistent. The citation is oddly vague about the venue or the date. The title sounds exactly like what you asked for, a little too exactly. The link is broken, or lands on a homepage instead of the article. The same source cannot be found by searching its title in a normal search engine.

The test is always the same and always cheap: find the source yourself, outside the chat, and read the actual words. If a source cannot survive being looked for, the answer built on it does not get to stand either. The hub page how do I catch an AI agent making up results goes deeper on the pattern.

Receipts for lookups: make the AI show its work

There is a stronger move than asking the AI to cite sources: have the lookups run as recorded calls. When research runs through tools on the Zambo MCP (https://zambo.dev/mcp, 153 tools, 35 on the default surface), each lookup returns a verifiable receipt at a public URL: what was fetched, what came back, and when, saved so anyone can recheck it free at zambo.dev/verify.

That changes the conversation. Instead of trusting that the AI checked, you hold the record of the check itself. A claim with no lookup behind it shows up as exactly that, a claim, and a claim with a receipt shows the source it rests on, as it was fetched, not as the AI remembers it. Zambo is the verifiable work layer for AI: this is the layer doing its job on an ordinary research task. A Day Pass is $0.99 one time and covers 24 hours. The Zambo Pass is $29 a month or $290 a year, and $19 a month for $ZAMBO holders. Humans pay by PayPal or card through PayPal; agents pay USDC on Base via x402.

When to stop trusting an answer

Stop when the pattern turns, not when a single fact wobbles. One corrected date is a fix; three invented sources in one answer is a verdict on the answer, and on the session that produced it. Stop when the AI defends a claim after you show it the source saying otherwise, when it produces new citations faster than you can fail them, or when the stakes are high, money, health, legal deadlines, and the answer rests on lookups nobody recorded. In those cases, start fresh, run the lookups as recorded calls, or take the question to a human whose name goes on the answer.

The habit to keep is simple: trust is earned per answer, in the open, with sources you opened and records you can recheck. Anything less is just a well-written guess.

Honest limits

Fact-checking catches a lot, not everything. A source can be real, current, and still wrong; two sources can copy the same error; and some questions have no settled answer to check against. Receipts prove what the AI fetched was not changed after the fetch; they do not prove the fetched page was true. For decisions with real consequences, these checks are the first pass, not the last word, and a qualified human stays in the loop.

Frequently asked questions

How do I fact-check an AI answer quickly?

Ask where each key claim came from and open the sources yourself. Check the date on anything that can change, rephrase the question in a fresh chat and see whether the answer holds its shape, and redo any simple math with a calculator. Most bad answers fail one of those in under a minute. For answers that matter, have the lookups run as recorded calls so you hold a receipt of what was actually fetched.

How can I tell if an AI invented a source?

Try to find the source yourself, outside the chat. Made-up sources tend to have vague venues and dates, titles that mirror your question a little too perfectly, and links that are broken or land on a homepage. If a search for the exact title finds nothing, treat the citation as invented and the claim resting on it as unsupported until a real source turns up.

What is a receipt for an AI lookup?

When an AI runs a lookup through a tool on the Zambo MCP, the call returns a verifiable receipt: a public record of what was fetched and what came back, fixed at the moment it ran. Anyone can open it and recheck free at https://zambo.dev/verify/ that the saved result was not changed afterwards. Claims backed by receipts rest on records; claims without them rest on the AI's word.

Does a receipt prove the AI answer is true?

No. A receipt proves the lookup result was not changed after the fact and shows exactly what the AI fetched. The fetched page could still be wrong, and the AI could still draw a bad conclusion from good sources. The receipt makes fact-checking possible on evidence instead of memory, which is most of the battle, but the judgment stays yours.

When should I stop trusting an AI answer?

When the pattern turns: several invented or misquoted sources in one answer, the AI defending a claim after you show it the source saying otherwise, or high-stakes questions, money, health, legal deadlines, resting on lookups nobody recorded. Restart with recorded calls, or take it to a human who signs their work. And for everyday questions, keep the one-minute checks as a habit rather than an emergency measure.

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