Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint, idempotentHint, and openWorldHint. Description adds that it compares current outputs to MLCommons benchmarks, returns structured drift metrics with statistical significance, and sources data from public APIs. This enriches behavioral context beyond annotations without contradiction.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.