> Dynamic languages have the same type of complexity, but you are not aware of it because it is well hidden

I would say you can ignore it until it fails in production.

I would HOPE it fails in production. Even better is if you don't validate your response data and suddenly send the wrong data, no data or in the wrong format.

Your consumers will love you for it.

Of course you can build your own schema + validation logic... or just accept static types and get it for free.