Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. 'Returns' implies a read-only operation and it discloses the shape of the returned board (ordered columns containing cards), which partially compensates for the absent output schema. However, it says nothing about permissions, empty-board behavior, or data freshness.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.