Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnly, idempotent, and non-destructive behavior. The description adds useful conditional behavior: when all providers are connected it returns authenticated true and empty pending[], while missing credentials cause it to return a connect_url and per-install URLs. This is meaningful beyond the annotation fields.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.