Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations are neutral (all flags false), so the description carries the behavioral burden. It adds the key trait that output is a PNG image and that content may be URL, text, or vCard. It does not disclose return mechanics (file path vs. binary vs. base64), but for a simple generate tool the disclosed traits are the most relevant. No contradiction with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.