What is Eval
A repeatable test of an AI system’s output quality, run to check whether a change made the answers better or worse.
In plain terms
Code either works or it does not, so an ordinary test gives a yes or a no. Model output is a matter of degree, so teams build evals: a fixed set of inputs, a way to grade the answers, and a score to compare across changes. The grading is done by people, by rules, or by another model. Teams that run evals can tell whether a change helped, and teams without them are guessing.
What it tells you about a developer
Eval experience marks a developer who has taken an AI feature past the demo into something a company can maintain. It is one of the clearest signs of an AI team that ships rather than prototypes.