It is not. You sent the base64 encoded image as text.
You did something like,
{
"type": "text",
"text": f"data:image/jpeg;base64,{base64_image}"
}
But you need to do,
{
"type": "image_url",
"image_url": {
"url": f"data:image/jpeg;base64,{base64_image}"
}
}