Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already disclose non-destructive, idempotent, closed-world behavior, so the safety profile is covered. The description adds only the '(seconds)' unit; it does not say whether setting a time outside the loaded range is clamped or errors, nor whether playback must be paused first.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.