Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses the substring matching approach, which is useful, but omits whether this is a read-only lookup, how matches are ranked/limited, whether matching is case-sensitive, and whether results include icons or metadata.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.