Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, so the description isn't burdened with safety. It adds behavioral detail that the data is 'gold-standard' and 'audited', that the name filter is case-insensitive (though schema also says this), and that franchise IDs link to content_enrichment. This goes beyond the basic read-only declaration.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.