This documents the profiles, extensions, value sets, and code systems defined by the HL7 tooling. Principally, this is the Java validator and the IG publisher, though these resources are used by other tools as well.
There is no expectation that these resources are applicable to real world healthcare systems.
https://build.fhir.org/ig/FHIR/fhir-tools-ig
This IG is used when building all IGs, and is always in scope for internal tooling reasons.