Hey there! TomTom Dev Advocate here! As the response above said, the SDK for Web and the Routing API are the best ways to get started building your application. You can also check out this article from our Dev Blog on using React native with our maps.
I wanted to reach out in this reply also about your email experience. You can absolutely use the SDK for Web from the Dev Portal build a directions-based application. If you have further questions and I can help clarify or understand better, feel free to DM me!
I'm wondering if there was perhaps a miscommunication as to the scale or type of app you're wanting to build. Regardless, happy to help. :)
Meanwhile -- here's also a functional example of Routing with Directions, so you can see a preview of those features too.
Link to tutorial here: https://developer.tomtom.com/maps-sdk-web-js/tutorials-use-cases/pizza-delivery
This tutorial shows you how to use the TomTom Maps SDK for Web to create a web application that helps a pizza chain select from which restaurant a pizza should be delivered to the customer.