Recently I had to work on developing an integration between MPOS and a CRM application via Retail Server/CRT. The REST APIs provided where JSON based and I needed C# classes to deserialize the response.
My gut feel said that there should be a tool to do this and I need not create the required classes and properties manually.
Sure enough after some web search, I found http://json2csharp.com/
This is an awesome site where you can provide a sample JSON API response and get the C# classes that can be used to deserialize the JSON.
Hope this helps you save some time, just as it helped me.