Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, and non-open-world, so the safety profile is covered. The description still adds value beyond them: it specifies the allowed domain scope ('Only paths on myaiguide.co are allowed') and the return nature ('readable text content', implying extraction rather than raw HTML). Both are useful and not derivable from annotations or schema.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.