Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must carry the full behavioral burden. The verb 'List' and the scope 'this user's' strongly imply a read-only operation with no side effects. The description also clarifies that it returns the user's own workspaces, which is a useful behavioral constraint. It does not explicitly state 'does not modify data' or mention pagination, but for such a simple read operation, the description is reasonably transparent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.