Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description adds useful behavioral limits: deterministic gating, sourced reasons, explicit unknowns, hosting conflicts, no performance scores, no account-access guarantee, no inference/purchase/setup action, and a clarification about no-new-subscription.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.