Why it matters for your business
Without evals, nobody can say whether an AI system is getting better or worse, and every change is a guess. A modest set of real examples, including tricky edge cases and questions the system should refuse, turns subjective impressions into a pass rate you can track. Evals make it safer to switch to a newer or cheaper model, because you compare results on your own tasks rather than on public benchmarks. When buying or commissioning AI work, ask to see the eval set and the results.
Example
Before launching an invoice extraction workflow, an operations team assembles 200 past invoices whose correct values are already in the accounting system. Each prompt or model change is scored on how many fields match exactly. When a newer, cheaper model is released, the team runs the same set and switches only if it matches the current model's accuracy.