Harmony leverages a 'contract first' design aproach. Rather than designing the internals of a service and generating the interface, we recommend that  you start with the outside and work your way in. 

Servcie Design starts off by identifying the reuse potential of a service. By understanding who the potential consumers are we can think about how they would like to see the service consumed. From here, service contracts are defined focusing on both message definition and non-functional policies.  The designer is responsible for maintaining the integrity of the service.  Loose coupling and other best practices are incorporated into the final design.

Designers are encouraged to create their own test cases for each service. In addition, we recommend that a 'dummy service' be created to mimic the functionality of the future service. This allows development teams that need to consume the service to begin coding to the dummy service facilitating parallel development between consumer teams and provider teams.