Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond annotations (readOnlyHint=false, destructiveHint=false), the description discloses key behavioral traits: always returns verification_pending, cannot be used to discover existing accounts, verification email sent only if address is free, nothing attached until link opened. It also notes rate limits and karma requirement. No contradictions with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.