Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With annotations already providing readOnly, idempotent, and non-destructive hints, the description adds valuable interpretation context: a zero flash count means a quiet observation within the window, not a data gap, and the `summary` field is ready to use. It also explains the temporal/spatial window of the data, which is not in the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.