Add output fields to an Output transformation to define the data fields you want to pass from the Mapplet to the downstream transformation. You must add at least one output field to each Output transformation.
Add output fields on the Output Fields tab of the properties panel. To add a field, click Add Field, and then enter the field name, data type, precision, and scale.
When you use the mapplet in a Mapplet transformation, map at least one output field to the downstream transformation.