Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and open-world. The description adds genuinely non-obvious behavior: query-based resolution silently picks the FIRST matching live listing, which is a caveat an agent would not otherwise know. It stops short of covering ordering criteria or pagination, so not a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.