Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds real behavioral context beyond that: it discloses the return value (an on-chain seal) and the auth requirement ('no key needed'), which an agent needs to know it can call this without credentials. It stops short of describing failure behavior or rate limits.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.