Resources or examples of current practices for communicating from a storefront to an app?

Shopify Partner
10 0 1

Hi all, I'm working on converting an old Express Shopify app I built several years ago to the new framework using Polaris/React, and I'm curious if anyone has any info on the current way to send data from the storefront to the app? When I first built the app I'm updating, you could specify a URL for an embedded app that you could send requests to (something like '/tools/myapp') so if, for example, you wanted to allow a customer to update metafields on their own profile you could include a form that would post to '/tools/myapp/update' or something similar which would be the equivalent of sending the request to ''.

I don't see anywhere in the current app setup where you would define that anymore, so I'm hoping someone could point me to some official documentation showing how I might go about doing something like that. I'm admittedly a little out of date and I'm learning React while doing the development so I may just be overlooking something obvious here, but any help would be appreciated. Thanks!