Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description discloses the 10-Zooq-credit cost and explains that slug resolution is included at no extra credit cost, or that a numeric id skips the lookup. Annotations already cover read-only/idempotent behavior, so the description adds useful non-obvious details beyond them.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.