Right now, every call on the buildWithParameters URL will always redirect to the job page on success. If this API is queried through an Ajax call, it should return a JSON output of the current job instead. This can easily be detected based on the Content-Type http header sent by the client.
This is useful for example if one wants to trigger a parametrized build from jQuery, and parse the result. Right now, jQuery will always get back the HTML page of the job, which makes it hard to do any error handling.