Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide readOnlyHint, idempotentHint, and destructiveHint. The description adds useful behavioral context: progress is 'durable' but 'respecting the website progress reset,' and assignment/study-plan summaries are only included 'when their separate permissions are granted.'
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.