How to add a GET param in a url endpoint, into an "executeBatch" request?

Hello,

I would like to use this sequence of requests into an executeBatch request but the second request return an error :

INPUT:

[{

         "key": "mystreams",

         "request": {

             "method": "GET",

             "endpoint": "/people/11065/streams"

         }

     }, {

         "key": "mystreamactivity",

         "request": {

             "method": "GET",

            "endpoint": "${mystreams:$.list[0].resources.activity.ref}?filter=notifications"

         }

     }]

OUTPUT :

{

...

}

{

  "id" : "mystreamactivity",

  "href" : "${mystreams:$.list[0].resources.activity.ref}?filter=notifications",

  "status" : 400,

  "error" : {

    "message" : "Bad Request. Improper URI syntax.",

    "code" : "400"

  }