Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Adds rich behavioral context beyond annotations: state transitions (ACTIVE if capacity, else PENDING), no billing side effects, no historical backfill, and monitoring alert synchronization. Annotations already declare a non-read-only, non-destructive operation; the description elaborates on the exact mutation semantics.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.