One of the functionalities significantly extending the potential of WEBCON BPS is the possibility of using the REST API interface. This article describes how to configure a data source based on information returned by the external services that provide their API. An example of using a REST data source can be a “Contractors” data source – connecting the source from an external system can keep the data up-to-date. Another example is the use of API provided by WEBCON BPS to display a data table based on a report from the Portal. The use of REST data sources may cause a break in the operation of the service prevents the use of the form.