Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden. It does disclose one important trait: browser-first tools return a client execution plan rather than a direct result. However, it does not describe side effects, execution mode selection, authentication needs, or what happens for non-browser tools.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.