Причин: retrofit.RetrofitError: метод POST должен иметь тело запроса

Я использую retrofit для создания сообщения api, я получаю следующую ошибку при попытке попасть в конечную точку.

     Caused by: rx.exceptions.OnErrorNotImplementedException: method POST must have a request body.
            at rx.Observable$30.onError(Observable.java:7334)
            at rx.observers.SafeSubscriber._onError(SafeSubscriber.java:154)
            at rx.observers.SafeSubscriber.onError(SafeSubscriber.java:111)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:197)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:173)
            at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at 
     Caused by: java.lang.IllegalArgumentException: method POST must have a request body.
            at com.squareup.okhttp.Request$Builder.method(Request.java:236)
            at retrofit.client.OkClient.createRequest(OkClient.java:59)
            at retrofit.client.OkClient.execute(OkClient.java:53)
            at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:326)

пытается получить доступ к сообщению api

 @POST("/service/v2/auth/ip-address")
    rx.Observable<AuthState> verifyIP();

фактический вызов api

LoginService service = CKRestClient.get().create(LoginService.class);
            service.verifyIP().observeOn(AndroidSchedulers.mainThread()).subscribe(
                    new Action1<AuthState>() {
                        @Override
                        public void call(AuthState authState) {

                        }
                    });
        });

Ответы

@POST("/service/v2/auth/ip-address")
rx.Observable<AuthState> verifyIP(@Body Object dummy);

LoginService service = CKRestClient.get().create(LoginService.class);

service.verifyIP(null).observeOn(AndroidSchedulers.mainThread()).subscribe(
  new Action1<AuthState>() {
    @Override
    public void call(AuthState authState) {
      // ...
    }
  });
});

@POST("/my/url/path")
Result postToServer(
        @Query("user_name") String userName);

@FormUrlEncoded
@POST("/my/url/path")
Result postToServer(
        @Field("user_name") String userName);

Result postToServer(@Path("my_path") String myPath,
                               @Body String emptyString);

restClient.postToServer(myPath, "");