Now that we have Pocket, is there any way to abstract the attributes to do Instapaper as well? Their API is pretty straightforward.

Yes, someone could use the same attributes to support Instapaper via our API.

I also use Instapaper. So it sounds like I’d have to write my own app to connect the exist API with instapaper’s?

I’ve made a self-hosted solution for anyone who is interested in tracking their Instapaper read article count through Exist. https://codeberg.org/da/exist.io-instapaper/src/branch/main#readme