Sending custom parameters on form submit GET response

Hello all, I am trying to create a login page. This is done using my authentication API, which requires some parameters passed into the GET request. I have added these parameters onto the action URL in the form submit settings. However, the form doesn't seem to be sending these parameters, only appending the username and password values from my form onto the base of the action url. Is there a way I can pass these other required parameters as part of the form submission?