Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Adds substantial context beyond the annotations: ~60s latency, ~$0.25 engine cost, billing with plan margin, budgetUsd capping behavior, chargedUsd as the cost report, and the required write scope. These are exactly the operational facts an agent needs before committing to an expensive call and align with readOnlyHint=false.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.