Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate readOnlyHint=true, so the agent knows it's a read operation. The description adds context about the kind of data (Prometheus-style metric exporters) but does not disclose return format, pagination, or limits. With annotations, the description adds some value but not rich behavioral context.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.