Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, non-destructive, closed-world behavior, so the description does not need to repeat safety. It adds valuable behavioral nuance by specifying that "usuarios" is the sum of daily users, not unique users for the period—a subtle but important detail for correct interpretation. It does not cover data freshness or timezone handling, but that is a minor gap given the annotations and output schema.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.