Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish read-only, idempotent, non-destructive behavior. The description adds useful behavioral context beyond those hints: it reveals the underlying Voyager GraphQL route, the REST-alias, pagination with next_cursor, and the semantic meaning of returned IDs for cross-tool flows. It does not disclose rate limits or default ordering, but the annotation bar lowers the burden.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.