Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden but says only that it 'loads' a page. It does not disclose auth requirements, rate limits, whether extraction is dynamic/JS-rendered, what the 'instructions' parameter controls, or what the result looks like.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.