Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnlyHint and openWorldHint, so safety is known. The description adds value beyond that by disclosing that results are capped and that the storefront URL is fixed (no per-store URL input), which materially shapes what the agent gets back. It does not quantify the cap, but that ladders to the limit param.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.