A sanity check is a quick test of whether a result is plausible at all, done before you rely on it or pass it on. It does not prove a result right; it catches the obviously wrong, such as a total ten times too large or a reply addressed to the wrong person. It takes seconds.
Why does a sanity check matter with AI agents?
Agents write confidently whether they are right or wrong. A draft with a misplaced decimal point reads just as fluently as a correct one. A few seconds asking "does this make sense?" before approving catches the gross errors that a fluent draft hides.
It is also the first habit employers look for in anyone handling numbers or customer outcomes. In an interview, describing your sanity checks shows you do not take output on trust, whether it comes from an agent, a spreadsheet or a colleague.
How does a sanity check work in practice?
Keep a handful of quick tests for each kind of work and apply them before anything else:
- Size: is the amount in the range you would expect for this kind of case?
- Direction: is money going the right way, is the customer being credited rather than charged?
- Who: is the name, account or address the right one for this case?
- When: are dates in the right order and in the right future or past?
- Sum: do the parts add up to the total?
If any test fails, stop and look properly. If all pass, move on to the full review. A sanity check is a filter, not a substitute for checking the evidence.
What is an example?
An agent at a utility drafts a final bill for a customer moving house. A reviewer we will call Priya glances at it first: the final bill is 2,400, while the customer's monthly bills have been around 80. That fails the size test immediately. Looking closer, she finds the agent used an estimated meter reading from a different property with a similar address. Without the sanity check she might have reviewed the wording, the dates and the address, all correct, and approved. With it, the problem was visible in seconds.
How is a sanity check different from a quality check or a four-eyes check?
A sanity check is quick, informal and done by the person handling the work, in the moment. A quality check is structured, done against a written standard, usually by someone else and often later on a sample; it is explained in what a quality check is. A four-eyes check is a formal second approval by an independent person before a sensitive action takes effect, covered in what a four-eyes check is.
Each catches different errors. Sanity checks catch the obvious; quality checks catch the systematic; four-eyes checks stop one person acting alone on something that matters.
Which terms are related?
- Plausibility check: another name for the same idea.
- Reasonableness test: a sanity check used in accounting and audit.
- Credit check: a different thing altogether, a look at someone's credit history, discussed in whether an AI agent can run a credit check.
For the full set of skills employers test, read AI skills for job seekers.
Questions people ask
Should an employer sanity-check a certificate on a CV?
Yes, and then verify it properly. A quick look for an issuer, a number and an expiry is the sanity check; checking it at source is the real test. Both steps are set out in how an employer checks an AI operator certificate.
How do I describe my sanity checks in an interview?
Name the quick tests you use in your current work and give one example where one caught a mistake. Interviewers want to hear that the habit is automatic, not occasional.