Best way of Implementing a logic + Content API

I have a bunch of Article pages which I can query using Content API.

I also have a separate Page type that has a Content Area property. This Content Area property holds Article pages.

The need is when I query an Article page, If that article page is part of Content Area then I need to dynamically add a property to response, probably boolean value that will indicate if the Article exists or not in the Content area.

I could possibly put some logic in TransformContent method, fetch the page type and its content and do a verification if the current article is part of content area then add the flag. Wondering if there is any better approach to do this.