Just noticed, that there is no way to add to watchlist using v4...

Hi @kironet, indeed. For most account functionality you're probably best to use v3. There is a covenient conversion method though, that you can use to create a v3 session from a v4 token.

Thanks @travisbell , is there a way to check if sessionid/access_token is still valid? I mean, how do I check if user removed my app from their tmdb account?