Evaluation as API is the API-first version of evaluation infrastructure. It means evaluation can be invoked, queried, compared, and acted on programmatically by CI systems, product workflows, agents, notebooks, and internal tools.
This is distinct from the phrase "evals as APIs" mostly in emphasis. "Evals as APIs" names the pattern. "Evaluation as API" describes the interface: structured inputs, structured outputs, stable evaluator IDs, experiment IDs, trace links, score explanations, and action hooks.