Maybe we're just talking past each other, but this is the entire point of a smart contract platform. I deploy code to it, and you now have a guarantee forever on the interface of that code, as well as its implementation logic. If I'm running the same code on my server and you're hitting my API, then I can change the interface, change the logic, or mutate the data in ways not specified by that code.

So really when I say "applications" I'm referring specifically to other smart contracts.