callfire webhook gives empty response

I have created Web hook For Outbound resource on event finished

curl -u username:password -H "Content-Type:application/json" -X POST "" -d '
    "name":"Call sent",
    "callback":"here is my call back url and it is https"

webhook is created successfully and i have checked in swagger
and the url is also get hit when oubound call is finished
but issue is that i am getting blank response i should get the below response
"webhookName":"Test Webhook",
"Test Label 1",
"Test Label 2"

here its doc link

Source: stackoverflow-php