The URI used to represent the vocabulary (in the $vocabulary keyword) SHOULD resolve to a document (not a schema, but any sort of plain text document that describes the vocabulary - ranging from a freeform README right up to a formal specification), that need not be publicly be resolvable, but SHOULD be resolvable in the context where it is intended to be used -- for example, if a company develops a vocabulary for its private use, then the vocabulary URI need not be publicly available, but SHOULD be available on its own private network as a description of that vocabulary. Note "SHOULD" not "MUST" -- this is just a recommended best practice but there may be reasons why it can't be done in all circumstances.

This also serves to clarify that the vocabulary URIs are NOT necessarily metaschemas themselves (which was raised as a question in an earlier issue).

At the locations of the draft vocabularies that we publish ourselves (e.g. https://json-schema.org/draft/2020-12/vocab/core), we could create short documents that summarized the intent of the vocabulary and linked back to the spec document that formally describes them.