Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description adds behavioral context beyond annotations (readOnlyHint, openWorldHint) by specifying the types of checks performed: syntax, domain, and deliverability. It implies external lookups (openWorldHint) without contradicting annotations. However, it does not disclose potential failure modes or cost implications.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.