code: function defaultArgsProvider(request, callback) {
      var args  = request.args,
          params = request.command.params;
  
      for (var i = 0; i < params.length; i++) {
          var param = params[i];
  
          // If the parameter is already valid, then don't ask for it anymore.
          if (request.getParamStatus(param) != Status.VALID ||
              // Ask for optional parameters as well.
              param.defaultValue === null) 
          {
              var paramPrompt = param.description;
              if (param.defaultValue === null) {
                  paramPrompt += " (optional)";
              }
              var value = prompt(paramPrompt, param.defaultValue || "");
              // No value but required -> nope.
              if (!value) {
                  callback();
                  return;
              } else {
                  args[param.name] = value;
              }           
          }
      }
      callback();
  }
docs: Default ArgumentProvider that is used if no ArgumentProvider is provided
  by the command's sender.