Just advertise the API in the headers. Or better yet, set the buttons/links only to be accessible via .usetheapi-dammit selector. Lastly, provide an API and a “developers.whatever.com” domain to report issues with the API, get API keys, and pay for more requests. It should be pretty easy to setup, especially if there’s an internal API available behind the frontend already. I’d venture a dev team could devote 20% to a few sprints and have an MVP thing up and running.