Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely new context: the property name is only returned where the operator's unit titles share it, and per-unit availability enrichment only occurs when dates are supplied, with a documented cap of up to 30 units.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.