Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds useful context about what the tool does NOT return (not a computed quote, base rate lives elsewhere), which is valuable. It doesn't describe pagination or response shape, but the output schema exists and the read-only nature is already annotated.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.