Use something like JSON-LD, where the payload contains hyperlinks to documents for each data property. Your client then can machine read that documentation (wh

Use something like JSON-LD, where the payload contains hyperlinks to documents for each data property. Your client then can machine read that documentation (which can have long-lived cache headers or be immutable, so your client doesn't spend it's whole time re-checking documentation). There will be a set of definitions that the client understood when it was coded, and by checking a payload for matching meanings, it can consume the information. If it finds something it doesn't understand, it could even try to take some compensating action (e.g. suppose it's a client which displays images to it's users, and it encounters a new type of image format. It could perhaps look up a registry of javascript canvas image renderers and download suitable code to display the new image).