Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety needs no restating. The description adds real behavioral context: this is a 'curated public subset', i.e. results are not authoritative for availability or installed status, which is a meaningful limitation the annotations do not convey. It stops short of stating pagination or whether the catalog is cached/static.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.