Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the idempotentHint and destructiveHint annotations, the description adds concrete semantics: already-existing tasks are listed and not recreated (explaining the idempotency in practice), the exact-name-match assignee rule, the fallback to unassigned with a reason, and the pointer to a removal call. This is rich behavioral context not derivable from annotations alone.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.