Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses what metadata is returned (source, date computed, licence, citation), which is the meaningful behavior for a zero-parameter metadata lookup, but says nothing about auth requirements, caching, or whether the values are static. For an inherently side-effect-free read this is adequate, not rich.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.