Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already convey read-only, idempotent, non-destructive behavior. The description adds useful behavioral context: it notes that raw binaries are not proxied and that the plain-text chunks are 'untrusted', which informs the agent about link reliability. It also scopes to 'current public' attachments, giving a temporal constraint. This adds value beyond the annotation profile.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.