How to create a custom resource with Services-3.x
All the documentation for the hook is in the services.services.api.php file included with the module. The args array is:


  an array describing the arguments which should be passed to this resource when it is called. Each element in the array is an associative array containing the following keys:
  
  
  name: The name of this argument.
  type: The data type of this argument (int, string, array)
  description: Text describing this argument's usage.
  optional: A boolean indicating whether or not this argument is optional.
  source: Where this argument should be retrieved from. This can be 'data' (indicating the POST data), 'param' (indicating the query string) or 'path' (indicating the url path). In the case of path, an additional parameter must be passed indicating the index to be used.
  default value: this is a value that will be passed to the method for this particular argument if no argument value is passed
  


There are a fair few examples in that file it might be worth giving them a read through, although the API documentation does actually specifically refer to the link you posted above as a detailed example of creating a new resource.