Evaluate an agent

Start with the cheapest evidence that can decide whether the agent did its job. Use code for exact facts, runtime tests for execution contracts, and a model judge for semantic quality that code cannot reliably decide.

Question	Evidence	Guide
Does this tool return the right value?	Direct unit test	Test layers
Does policy block a write?	Full runtime trajectory and unchanged domain state	Authority
Does the agent handle a representative request?	A fresh candidate run with stable assertions	First evaluation
Is the answer grounded and useful?	Evidence-based rubric with a qualified judge	Quality judgments
What happened in a retained session?	Historical trajectory evaluation	Production evaluation
Did a release regress?	Compatible baseline and candidate result	CI workflow

Keep evaluator failure separate from candidate failure. Missing evidence cannot establish a pass. A historical judgment does not execute changed code, and a deterministic provider does not establish live-model answer quality.