Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond annotations (readOnlyHint=true, idempotentHint=true, destructiveHint=false), the description adds concrete side-effect guarantees: 'requires no account', 'creates no quote or task', and 'moves no funds'. It also describes the normalization/deduplication behavior, which is not present in annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.