Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide readOnlyHint=false, destructiveHint=false, etc. The description adds valuable behavioral context beyond these, such as automatic routing and that messages appear in a shared conversation visible to the renter, which informs the agent of potential visibility consequences. No contradictions with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.