Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint and openWorldHint, so the safety profile is clear. The description adds meaningful details about the return content (carrier, line type, country, validity). It does not contradict annotations, but it also does not disclose caveats such as data availability by region, external lookup behavior, or potential variability, which would have been valuable context.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.