Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnly, openWorld, idempotent, and non-destructive behavior. The description adds valuable detail beyond that: no charge when splits are unavailable, upstream 400 errors for unsupported sports, and the bookmaker slug mapping convention relative to get_odds.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.