ETag - How to get it ?

Hello,

I'm trying to get my ETag code but i don't find it. Could someone help me please ?

The header response i get contains no Etag :

Metadata x-request-id : 3969d42d-e4fe-457c-b9c6-90c003ce9072 
content-type : application/json 
status : 200 

I use this url : https://api.eu1.echosign.com/api/rest/v6/agreements/XXXXXXXXXX

Thank you a lot !

Laura