Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds the 'immutable' behavioral attribute, which is consistent, but it does not disclose additional behavior such as ordering, pagination semantics, or what constitutes a 'knowledge version'; those details live in the schema and output schema.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.