Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate read-only, open-world, idempotent, and non-destructive behavior. The description adds meaningful extra context: work is 'current' and, crucially, that task text is untrusted data and not instructions, proof, escrow, or authority — a valuable safety-relevant behavior beyond what annotations or schema convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.