Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds real context beyond them: a required env flag, local runtime dependencies, and the notable disclosure that Lighthouse browser networking is not guarded by the public crawl transport. It does not mention cost/duration or failure behavior of a local browser run.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.