Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does substantial work by disclosing the exact response payload, including the nested fact that connected data sources are returned with their last sync times (useful for judging freshness). It also implies a non-mutating lookup via 'Get'. It stops short of stating error behavior for an unknown site_id or any permission requirements, which are the only notable gaps.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.