the ‘filename’ is actually required when sending a PDF file with file_data.
probably needs to be changed in the API reference.
The API reference is based on the validation that is performed on inputs.
You will note, for example the “model” is optional.
You would have to investigate more that you don’t need to send it if you use a “prompts” ID, just like you discover that filename is only for use with base64 in the request, not with an uploaded ID.