payload.json

{
    "image_url": "http://dev.iron.io/images/iron_pony.png",
    "operations": [
        {
            "op": "sketch",
            "format": "jpg",
            "destination": "sketch.jpg"
        }
    ],
    "aws": {
        "access_key": "MY ACCESS KEY",
        "secret_key": "MY SECRET KEY",
        "s3_bucket_name": "MY BUCKET NAME"
    }
}