Secondly ServiceStack promotes using Request and Response DTO’s whereas this looks a lot like a WCF-style RPC Service. To learn more about creating message-based Web Services in ServiceStack and how it differs with WCF and Web API, see these earlier StackOverflow answers:
Once you can define a ServiceStack Service they’re easily consumable using ServiceStack’s .NET generic Service Clients which lets you re-use the Server DTO’s which gives you an end-to-end typed API without code-gen.
You can also use Add ServiceStack Reference for an alternative solution for generating typed DTO’s for different languages/platforms from a remote ServiceStack instance.