Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate read-only, non-destructive, closed-world behavior, and the description adds important operational context beyond them: the call runs four parallel AI completions server-side, is expensive, and persists nothing. That persistence note is especially valuable because it explains why a separate save step and explicit user authorization are required.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.