Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The only behavioral detail added beyond the annotations is the Base64 encoding requirement, which is already present in the schema's parameter description. The description does not disclose what happens on success, whether there are file size limits, if the upload is asynchronous, or what the response contains. Since there is no output schema, this omission is significant.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.