A Practical Guide to Agent Evals: Don’t Just Look at What It Says—Look at What the World Becomes

Agent evals must verify not only the response, but whether the world actually changed. Anthropic shows how to combine graders, isolate environments, and maintain an eval suite over time—and why 20–50 real failures are enough to start.

Skillify: Turn Every Agent Failure Into Something Structurally Impossible to Repeat — Garry Tan's 10-Step Checklist

Garry Tan's agent screwed up twice this week — both bugs had the same shape: deterministic work done in latent space. His fix is skillify: every failure becomes a SKILL.md + deterministic script + tests + evals + resolver trigger. Ten steps. The bug becomes structurally impossible to repeat.