For body I fully agree. But for the "document" I'm not completely sure. You see, I was going to document the "document" like this:
        ```/**
         * Body of the response parsed into structured object
         *
         * @property document
         * @type {Object}
         * @default {}
         */```

I guess it will make more sense for developers, who will use it. And it will be hard to explain them, why Object is initialized by empty string, isn't it?