Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, destructiveHint=false and idempotentHint=false, so the safety profile is covered; the description adds value on top by disclosing the lifecycle side effect (dormant on creation, first scan auto-starts once assets exist) and the plan-limit failure mode with a limit-naming error. That is exactly the non-obvious behavior an agent needs before calling a mutating tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.