Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure. It says nothing about whether the scroll is smooth or instant, how far one invocation scrolls, whether it targets the page or a focused element, or whether any state is returned — all relevant for an agent deciding how many times to call it.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.