OpenAI API: image_url is only supported by certain models.

This OpenAI API error message:

Error: {
   "param": "messages.[1].content.[1].type",
    "message": "Invalid content type. image_url is only supported by certain models.",
    "code": null,
    "type": "invalid_request_error"
}

… is a (mistaken) catchall that’s likely covering up something else. The API returns this whenever there’s a problem in the image_url field, regardless of your model choice. (Try sending it garbage image data as base64 to test it.)