Services and service endpoints can specify the response serializer to use when the service endpoint constructs a reply. The serializer is responsible for producing the entire response including headers and the response body. This provides total flexibility and control over how the service responds.
The setting on the service is the default for all endpoints that do not specify a serializer. If the service does not specify a serializer then Json is the default.
The serializer is specified as a class type to use. This class type must implement the IResponseSerializer interface. There are implementations of this interface in the OwinFramework.Pages.Restful.Serializers namespace.