Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden. '(pro-only)' discloses a plan/permission constraint, which is genuine added value. But for a destructive mutation it says nothing about irreversibility, cascading effects on campaigns or lookalikes built on the segment, or success/failure semantics.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.