How to make a REST API request for CustomObjects on ACS

I receive: 'Failed to authenticate user' this is i doing: - first make a request for login an admin user, Ok - get a user id from the previous login and make a new request from Create CustomObjects URL: https://api.cloud.appcelerator.com/v1/objects/country/create.json?key=j8M?80n?N0P?3Z?AQ?R3y?wD?S8?VVKL Params: var params = { user_id: $id, fields: { code: $f1, name: $f2 } }; // $id (from the previous login), $f1, $f2 --> Javascript vars

And the API response is: "Failed to authenticate user"

What is wrong???

(Sorry for my bad drafting in English)