Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare a non-read-only, non-idempotent operation in an open world, so the agent knows it mutates external state. The description adds nothing: no indication of required permissions, what a created step is attached to, or what happens on retry given idempotentHint=false. It does not contradict the annotations, but it contributes no behavioral information at all.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.