The Designer is able to communicate with SAP servers via RFC and to exchange data via IDocs out of the box. You do not need any additional client libraries.
RFC Communication The SAP RFC (Remote Function Call) protocol is the most basic way of communicating with SAP offered by the Designer. With the Designer you can invoke RFC enabled ABAP programs as RFC functions.
IDoc Communication IDocs (Interface Documents) are the most common way of interchanging data asynchronously with SAP systems. With the Designer you can parse and compose IDocs.