Looking at https://webidl.spec.whatwg.org/ https://webidl.spec.whatwg.org/ I'm not sure if I understand how this really helps bridging type information from js

Looking at https://webidl.spec.whatwg.org/ https://webidl.spec.whatwg.org/ I'm not sure if I understand how this really helps bridging type information from js to python to c++ - it looks very tied to js? There's openapi (swagger) and json schema which seems more like helping define RPC over http?