Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=false and destructiveHint=false, so the mutating yet non-destructive nature is already structured. The description adds valuable behavioral context: it works for any widget type and that omitted dimensions are left unchanged (partial updates), which annotations do not convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.