Best solution for external data API

I have an external datasource for a few post_types that need their data to be pulled in externally. Mostly for “quality control” purposes for the Admin. I’m bringing in the data fine, I’m just wondering the best practices for integrating it into the WordPress Admin Panel.

Ideally I would have an “Update from Data Source” button on the post type, which when clicked, would make an ajax call to an API page on WordPress telling it to update that post from the external datasource.

The only way I can think of is to have a custom “API” page that would handle the query vars since I need to use WordPress’s hooks to update the data.

Is there a better way to do something like this? Or is there a way to have the WordPress helper functions loaded from an update.php file I create?