Right now you get different bindings depending on who calls the script. Some times the $message binding is the payload and sometimes its the MuleMessage instance. Not good. I suggest the following bindings: $muleContext MuleContext $eventContext MuleEventContext $message MuleMessage $log Logger if MuleMessage is passed in $payload MuleMessage.getPayload otherwise $originalPayload MuleEvent.getMessage.getPayload $payload MuleEvent.transformMessage() (all message headers get added to the context too) For backward compatability: $src = $payload