Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safe read-only, idempotent, non-destructive profile. The description adds useful behavioral context by saying the tool should only return a replacement when evidence exists and otherwise returns 'none identified', which helps prevent hallucinated replacements. It stops short of describing evidence sources or lookup behavior in more detail.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.