When an AI answer matters, do not just ask for the answer. Ask where it came from.
That does not mean asking for pages of hidden reasoning. Ask it to point to the exact paragraph, spreadsheet row, email, source or calculation that supports the conclusion. If it has added two figures together, ask it to show the calculation. If it has interpreted a document, ask for the passage it relied on.
This turns a plausible answer into something you can actually check. It also exposes problems quickly because a weak answer often becomes obvious the moment the supporting evidence is missing.
For anything involving money, contracts, performance or important decisions, “show me the evidence” is a very useful final instruction.