How to tell if an AI answer is reliable

Recompute the figure the answer depends on

Most costly mistakes come down to one number: the monthly payment, the tax due, the last legal day. Redo that one calculation with a calculator or a spreadsheet, not by rereading the answer.

A fluent explanation around a wrong figure is common. The formula is right; a step inside it is not.

Example check: Extra $300 a month on a $400k mortgage: an AI's maths, checked

Check that the rule is current and applies where you are

Tax allowances, visa rules and medical guidance change, and differ by country. Look for the year and the place the answer assumes. If it names neither, treat it as possibly out of date and check the official page.

Example check: Sold at a loss, bought back 16 days later: the wash-sale rule, checked

Find out how it counted

Rules such as “90 days in any 180” or “above 3% of your salary” depend on how you count: which days are included, what is added up, what is taken off first. An answer that adds numbers without saying how it counted is the one to recheck.

Example check: Back to Europe after 70 days? The 90/180 rule, checked

Get a second answer from a different company's AI

Ask a model from another company the same question before it sees the first answer, then compare. Where they disagree is where to look. Where they agree, the answer is more likely right, but still not proven.

Related guide: Why check an AI's answer with a different AI

Save the effort for what matters

Not every answer needs this. A recipe or a draft email can be fixed later. Money, health, legal deadlines and code you will ship are where a check pays for itself.