To override the Content-type in your clients, use the HTTP Accept Header, append  the .json suffix or  ?format=json
To embed the response in a jsonp callback, append ?callback=myCallback
        
        HTTP + JSON
         The following are sample HTTP requests and responses. 
            The placeholders shown need to be replaced with actual values.
POST /json/reply/CreateFileSystemItem HTTP/1.1 
Host: blazor-gallery.servicestack.net 
Accept: application/json
Content-Type: application/json
Content-Length: length
{"fileAccessType":"Public","file":{"id":0,"fileName":"String","filePath":"String","contentType":"String","contentLength":0,"fileSystemItemId":0}}
 
HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: length
{"id":0,"fileAccessType":"Public","file":{"id":0,"fileName":"String","filePath":"String","contentType":"String","contentLength":0,"fileSystemItemId":0},"appUserId":"String"}