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 only states 'Start browser instance' without revealing side effects (e.g., opening a new window, network access), whether it blocks, or what happens if called repeatedly. This is minimal and insufficient for an agent to anticipate consequences.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.