The importance of APIs
Since the rise of the cloud era, user expectations have changed quite dramatically. Customers want easy & direct access to their own virtual slices of the data center. For its part in making that happen, SDN provides APIs that make the networking part as responsive as users and their application workloads need it to be. Admins can define global policies, while customers can do whatever they want with their own part of the cloud.
And they do that through APIs.