Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnly, idempotent, openWorld and non-destructive. The description adds genuinely useful behavior beyond that: it fetches the page, detects existing types, returns ready-to-paste templates, pre-fills from metadata, and marks incomplete fields with FILL:. That return-shape and convention context is valuable.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.