The function must have no output parameters. All output must be in the return value. If you need to return multiple values, you should use such types as Structure, Array, etc.
// Incorrect:
ServiceURL = "";
UserName = "";
UserPassword = "";
FillConnectionParameters(ServiceURL, UserName, UserPassword);
// Correct:
ConnectionParameters = NewConnectionParameters();
// Returned value - Structure:
// Service URL - String
// UserName - String
// UserPassword - String