Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already mark this as non-read-only, non-destructive, and idempotent. The description adds valuable layer: the invoice remains viewable and financial documents are never permanently deleted, which prevents an agent from fearing data loss. This supplements the annotation profile usefully.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.