Adding custom properties to Ember Model

I'm trying to add a custom property to an Ember Data Model. Specifically I want to add a property which defines the REST end point to use in an Ember Data Adapter I'm writing.

My Model is defined as such (with custom property 'endPoint'):

import DS from 'ember-data';

export default DS.Model.extend({

partner_id      : DS.attr('string'),
partner_key     : DS.attr('string'),
partner_name    : DS.attr('string'),
created         : DS.attr('string'),
status          : DS.attr('string'),
type            : DS.attr('string'),

endPoint        : 'api_entry'

});

In my Adapter I'm trying to access the property as follows:

_buildURL: function (modelName, store, id, snapshot, requestType, query) {

    var host, namespace, url;

    var model = store.modelFor(modelName);

    var endPoint = model.endPoint;
    var endPoint2 = Ember.get(model, 'endPoint');

    console.log(endPoint, endPoint2);

    host = Ember.get(this, "host");
    namespace = Ember.get(this, "namespace");

    url = [];

    if (host) {
        url.push(host);
    }

    if (namespace) {
        url.push(namespace);
    }

    url.push(modelName);

    url = url.join("/");

    if (!host) {
    url = "/" + url;
    }

    return url;
},

In the console.log above, both endPoint and endPoint2 are undefined. I'm new to Ember and Javascript. What am I doing wrong? Is there a more 'Ember' way to do this? I don't want to use the actual REST endpoint names as my model names as they do not adhere to Ember model naming conventions.

Help much appreciated.