Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive behavior, but the description adds real behavioral context: reminders are resurfaced in the morning brief and optional brief email, inactive reminders are excluded by default, and delivery_note appears when the brief cadence prevents delivery. This goes beyond the structured annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.