Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It usefully discloses a real behavioral guardrail -- Map 1 (system default) cannot be deleted -- but omits whether deletion is permanent/irreversible, what happens to entities referencing the map, and any permission requirements.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.