Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so safety is covered. The description adds one genuinely useful behavioral fact not in the structured data: the workbook is returned as an embedded base64 resource rather than a path or stream. It says nothing about payload size limits, failure modes, or why this is restricted to remote servers.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.