You can have the most capable model, a well-engineered harness, and a solid product vision - and still have no idea if your agent is actually working. That's the problem evals solve. An evaluation ("eval") is a test for an AI system: give an AI an input, then apply grading logic to its output to measure success. Good evaluations help teams ship AI agents more confidently. Without them, it's easy to get stuck in reactive loops - catching issues only in production, where fixing