Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare destructiveHint=true, but the description adds nuance the annotation cannot: the layer's id, position, size, animations, styles and trim window are preserved, and only the source mp4 is replaced. It also flags the upload prerequisite. Useful context beyond the safety hints, though nothing on failure modes or permissions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.