Why is it bad idea to use Request::isJson instead of API route?

Hi,

Can someone explain to me in a nutshell why I should not be doing this in my existing laravel app?

I want to add json responses to use it in a native app. I have working controllers, routes etc.

Now not to rewrite the whole logic I figured that for a simple usage I can do just this:

if (\Request::isJson()) {
            return \Response::json(compact('articles', 'categories', 'colors', 'id'));
        } else {
            return view('homepage', compact('articles', 'categories', 'colors', 'id'));
        }

and get a nice json response that I will be using inside my iOS android app.

I have a feeling however that apart from obvious pagination, authentication and etc there is a much more to it.

What am I doing wrong please?