Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description adds significant detail beyond annotations: ordered turns, direction/role derivation, truncated boolean, message_count field, and behavior for brand-new messages. Annotations already indicate read-only, idempotent, non-destructive, and the description is consistent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.