Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, so the agent knows this is a safe read with no side effects. The description adds no further behavioral context (no auth requirement, no error/not-found behavior, no rate limits), but with annotations covering safety the lower bar makes a 3 reasonable.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.