Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only and non-destructive behavior. The description adds useful context about the returned data structure (sport id, slug, name, team-sport flag, leagues with current_season) that is not redundant with the output schema, and it clarifies the tool's scope beyond the hints.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.