This API uses OAuth authentication, this requires you to request an access token before successfully accessing the data behind the API.
You can get an Access Token by making a POST request to https://auth.storefeeder.com/connect/token with the following in the body of the request.
grant_type=password&username=example%40example.com&password=example&scope=sf.mobile.api+sfprofile+sfmobilefeatures&client_id=sf.mobile.c
The response from this request is always in JSON format, and includes an 'access_token' property which you can use in subsequent API requests by including the following header:
Authorization: Bearer {access_token}