Sophos SMS gateway required response format

Can anyone share complete details on SMS gateway response format. I had gone through docs. But documentation is not clear.

https://docs.sophos.com/nsg/sophos-firewall/18.5/Help/en-us/webhelp/onlinehelp/AdministratorHelp/Authentication/GuestUserSettings/AuthenticationSMSGatewayConfigure/index.html#enable-authentication-with-the-newly-created-sms-gateway

My previous post: https://community.sophos.com/sophos-xg-firewall/f/discussions/133211/sophos-xg-430-sms-gateway-integration-for-guest-registration

1. What is required response mime type ? JSON or XML ?

2. What are the required variables in response and their datatype ?

3. Why registered guests not listed in Authentication -> Guest Users ?

4. Please share the working response format.

Password type: Numeric only 6 digit.

My API produces below response:

{
"Status": "Success",
"Details": "ff9ab5b0-452e-11e7-94da-0200cd936042"
}

I recreated response format

{"Status":"{0}","Details":"{1}"}

Even after receiving username and password on mobile, users can't login