Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses that the information is 'published' and points to a specific source URL, implying a read-only retrieval with no side effects. However, it does not describe the response format, freshness, or any caveats about the static source, leaving some behavioral ambiguity.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.