Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate a non-read-only, idempotent, and destructive operation. The description adds useful behavioral constraints (base64 encoding, supported formats, 10MB limit, authentication requirement). It does not address the destructiveHint (e.g., possible overwriting), but given annotation availability, the description still adds value.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.