This document discusses how to transform a JSON payload into a different JSON format in Mule. It provides an example of transforming an input JSON with name and id fields into an output JSON that adds a designation field. The document recommends using an expression transformer to dynamically modify the input JSON and produce the transformed output JSON in Mule without needing the enterprise Datamapper component. It includes an example Mule flow that uses JSON transformers and set variables along with an expression transformer to transform one JSON payload into another with an additional field.