Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds meaningful behavioral context beyond annotations: it is a static reference, returns no live counts, reads no workspace data, and costs nothing. This fully sets expectations for a safe, side-effect-free tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.