An AI that checks another AI's work — because no model can mark its own homework
An AI can check another AI's work, and that is the only version of the check worth trusting: the reviewer has to be a different model, trained by a different lab. A model asked to review its own answer runs the same reasoning that produced the error, so it is blind in precisely the same direction — asked "are you sure?", it usually restates the claim with more confidence rather than finding the fault. Independence is the entire mechanism. Two models from rival labs rarely invent the same false fact, so where one fabricates, the other has a genuine chance of catching it.
Decidi is built on that separation. Any reply in free chat can be handed to a model from a different lab with one tap — Challenge — and it comes back with the specific problems named: an invented figure, a claim with nothing behind it, a logical gap the conclusion leans on, a caveat glossed over, a contradiction, or confidence the evidence does not support, plus a one-line verdict of solid or verify. Escalate and the same principle scales: rival frontier models — OpenAI GPT, Anthropic Claude, Google Gemini, xAI Grok — argue the question out across structured rounds with expert personas, a moderator synthesises one verdict, and then an always-on Final QA reviewer that took no part in the debate hunts the draft for fabricated citations, figures that do not reconcile and claims nobody can stand behind. That audit runs before you see the answer, not after you have acted on it.
- The checker is never the author — the audit is routed away from the lab that wrote the reply
- Flags are typed and specific: invented fact, unsupported claim, weak reasoning, missed caveat, contradiction, overconfidence
- A committed one-line verdict — solid, or verify these before you rely on it
- An always-on Final QA that reviews the verdict itself and took no part in producing it
- Fabricated specifics are stripped rather than smoothed over — a marked gap beats an invented citation
- Every calculation re-derived from the stated inputs, so the same figure cannot quietly disagree with itself
- Challenging an answer is free and needs no account, so a check costs you nothing to try
Part of: How Decidi works
A claim-by-claim audit of the AI answer you were about to rely on: what held, what broke, what looks invented, and the exact items to confirm against a primary source before you act.
Common questions
Can an AI check another AI's work?
Yes, and it is the only form of AI checking that reliably works. A model trained by a different lab, on different data, does not share the first model's blind spots — so a fabrication by one usually contradicts what the other knows, and that divergence is the detection signal. Decidi does exactly this: any chat reply can be audited by a model from a rival lab, and every full Multi-Agent run ends with a Final QA pass that took no part in the debate.
Why can't an AI check its own work?
Because it would use the same reasoning that produced the error. The model has no independent source to compare its answer against, and it is trained to be agreeable — so "are you sure?" typically returns the same claim, restated with more confidence. Self-checking catches typos and formatting slips. It does not catch a confident fabrication, which is the failure that actually costs you.
Does the checking model have to come from a different company?
It should. Models from the same family share training data, tuning and failure modes, so two of them agreeing is closer to asking one expert the same question twice than to a second opinion. Decidi's Challenge names the lab that wrote the reply and deliberately routes the audit elsewhere. On a full run the Final QA is a reviewer that argued no position in the debate, and on Deep runs it is drawn from a different lab to the model that chaired.
What does the check actually look for?
Six things, named rather than judged by feel: facts, citations or figures that look invented; claims asserted with no evidence behind them; a logical gap the conclusion leans on; a material caveat or exception the answer skips; two parts of the work that do not agree, including numbers that fail to reconcile; and a confident tone on something genuinely uncertain. It is equally bound not to manufacture problems — a fabricated flag is as dishonest as a fabricated fact — so work that is sound is told plainly that it is sound.
If a second model approves the answer, is it right?
No — it is a much stronger signal, not a guarantee. Independent models can still share a common misconception, and neither can verify a fact that lives only in a document neither has seen. Decidi handles that honestly by naming what it could not confirm: every verdict ends with a "verify before you rely on this" list itemising the citations, figures, dates and sources you must check against a primary source. Anything with legal, medical or financial consequence still deserves a qualified human sign-off.
What does it cost to have an AI answer checked?
Checking an answer is free and needs no account — paste in what another AI told you for a fast independent audit, or tap Challenge on a reply in chat, where the audit is deliberately routed to a model from a different lab than the one that wrote it. A full Multi-Agent run, where rival models debate the question and the Final QA signs off a downloadable deliverable, is priced per run rather than per token: Plus at $19/month includes 16 full runs a month, and Pro at $49/month includes 44. You are paying for a checked verdict, not for the words used to reach it.
Try it on your own decision
Start in chat free, with no account. When the answer matters, put it to GPT, Claude, Gemini and Grok — they debate it, a Final QA audit reviews it, and you get one clear verdict with the open questions named.
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