Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive behavior, so safety is covered. The description adds a genuine behavioral nuance — that it operates only on query-visible traffic — plus a caveat about single-period results, but says nothing about rate limits or output characteristics.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.