Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden, but it only states the action. It does not disclose whether the group must already be expanded, whether the collapse is a toggle, what happens if the group is not collapsible, or whether any UI state changes beyond the collapse occur.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.