[int_19h]

It is a standard in a sense that they will all read it (although last I checked you still need to adjust the default config with Gemini). But feature support varies between different tooling. For example, only Claude supports @including other files.

[WorldMaker]

The "standard" AGENTS.md suggestion for that is [regular markdown links](./like-this.md)

[int_19h]

The problem is that it doesn't actually include the referenced file in the context. The model will only see what's in it if it deigns to read it, but that's not a given in all circumstances where it might need to.

I use this feature often in Claude to bring specific files so that they are in context at all times. E.g. when working on a parser, I will often put the grammar to be always in context. Or if working on a web app, all the model types.