Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=true, and the description does not contradict this; the operation is a read-only decode. The description adds useful context by naming input sources and the exact output format. However, it does not disclose potential edge behaviors such as network access for URLs, size limits, or failure modes.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.