Filter attributes at rest module

Hi, all! I'm using rest module to connect to my java restful service with json format request. It works good, but i get troubles with EAP-TLS - it tries to encode ALL request content. How I can skip unused attributes (EAP-Message and other specific attrs). I have tried to use attr_filter module, but it do 'noop'. How I can limit attributes, that will be encoded to json?