Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, non-destructive and non-open-world behavior, so the safety profile is covered. The description adds genuine scope context beyond that: authentication, authorization, storage and deployment are host responsibilities described by the manifest, telling the agent what this call will not do. It still says nothing about size limits, pagination, or whether source files are inlined or referenced.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.