I keep trying to write docs but then I also keep making them out of date. The idea is that instead of each author of a tool like Pantograph building its own system of language support, (with each language author having to build support for each tool) our hope was that we could design some set of data structures, APIs, and capabilities which would allow a proper frontend/backend divide between languages and the the tools which consume their definitions.

The best place to get started is to see how CSTML works in the playground: https://bablr.org/playground. It's meant to be a self-describing format. It can be streamed, and we have a btree-backed storage format for it that makes incremental editing of immutable trees a breeze.