Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds non-obvious operational context beyond those annotations: cursor-based pagination, a 10-credit cost, and equivalence to another upstream endpoint. This is exactly the kind of additional behavioral detail that helps an agent invoke the tool correctly.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.