Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden. It usefully discloses data provenance ('source-linked watch over the curated Viridis dataset, not a live external regulatory feed'), which is real context. It says nothing about auth needs, result shape, pagination, or freshness limits.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.