Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The readOnlyHint annotation is consistent with the description's 'Read' verb, so no contradiction. The description adds useful context about the return contents (Canvas and Editor documents) beyond the annotation, but does not disclose other behavioral aspects like error conditions or response structure. With annotation covering safety, the added value is moderate.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.