Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations mark this read-only, and the description adds useful beyond-annotation context: public channels need no authentication, restricted channels need a bearer, and messages are returned newest first. However, the pagination note calls `before` the 'oldest msgid,' which conflicts with the schema's explicit 'timestamp field, not the msgid,' slightly reducing reliability.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.