Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden and does add useful access context: conversations are public, only named peers can write, everyone can read. However, it doesn't disclose return shape, pagination, ordering, or explicitly confirm this operation is read-only beyond the word 'Browse'.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.