create mobile app with rest for web app

I have a web app with rest endpoints. now i want to create a mobile app for it. Do i need to use Oauth authentication when i create the mobile app to access the rest points? I am not building a third party app but just a in house mobile app for the web app. I tried building it without access token authorization. As i understand it , once the user logs in , the rest points will be available for use without the need for access tokens.Since i have already authenticated the user thru login.