Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It lists what data will be returned, indicating a read operation, but does not explicitly state that it is read-only, nor does it disclose potential edge cases (e.g., what happens if neither slug nor id is provided, or if both are given).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.