Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description is consistent with the readOnlyHint=true annotation, stating a list operation. It adds useful scope ('all installed') and return content ('with their descriptions'), but does not disclose other behavior such as ordering, filtering, pagination, or error conditions. No contradiction.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.