Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds real value beyond that by disclosing conditional behavior ('when the infrastructure probe is available') and the scope of what is compared (parent vs child NS sets, AA responses, glue), which an agent could not infer from annotations alone.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.