Ask HN: What is your risk plan if your app is purely dependent on 3rd party API?

You build app around specific free API, for example some social media. Without this API, your app is useless as you can't just easily switch providers like with some weather app.

What is your risk plan, when some day you could be cut off from accessing API?

Do you make it modular enough, so when time come, you just switch to another API?

I'm asking, because for me, it always seemed like a big risk without some long term agreement.