Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are present, so the description must carry the burden. It adds the behavioral detail that only 'active' sessions are listed, but it does not state whether the operation is read-only, whether it has side effects, or what the response contains. The word 'list' implies read-only, but this is not explicit.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.