Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden. 'Get all products' clearly implies a read-only listing operation with no destructive effects, but it does not mention pagination, response shape, or any store-specific behavior that might affect an agent's expectations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.