Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full burden. It reveals that the tool returns total unread count and per-room breakdown, and limits to subscribed/member rooms. However, it does not disclose behavior like idempotency (implied by GET), error handling, or any side effects. It provides moderate transparency.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.