Have you checked https://github.com/mendix/RestServices/blob/master/README.md for the details about how to use the Rest Services Module? Try to format the response with Notepad++ or online like : https://jsonformatter.curiousconcept.com/
It will give you pointers how to construct the domain model for the response if you have a clear understanding of what the result looks like. Combine it with the manual of the rest services and you should be able to work it out.
{
"id":"cus7zhxyKnCmFeqmM",
"object":"customer",
"accountbalance":0,
"created":1456719719,
"currency":"usd",
"defaultsource":"card17jiXj2eZvKYlo2C8ZGQQOn0",
"delinquent":false,
"description":null,
"discount":null,
"email":"newvmedix+pat@gmail.com",
"livemode":false,
"metadata":{
},
"shipping":null,
"sources":{
"object":"list",
"data":[
{
"id":"card17jiXj2eZvKYlo2C8ZGQQOn0",
"object":"card",
"addresscity":null,
"addresscountry":null,
"addressline1":null,
"addressline1check":null,
"addressline2":null,
"addressstate":null,
"addresszip":null,
"addresszipcheck":null,
"brand":"Visa",
"country":"US",
"customer":"cus7zhxyKnCmFeqmM",
"cvccheck":"pass",
"dynamiclast4":null,
"expmonth":2,
"expyear":2016,
"funding":"credit",
"last4":"4242",
"metadata":{
},
"name":null,
"tokenizationmethod":null
}
],
"hasmore":false,
"totalcount":1,
"url":"/v1/customers/cus7zhxyKnCmFeqmM/sources"
},
"subscriptions":{
"object":"list",
"data":[
],
"has_more":false,
"total_count":0,
"url":"/v1/customers/cus_7zhxyKnCmFeqmM/subscriptions"
}
}