What do you mean by excessively verbose? They seem to make a point at being minimalist and the comparison with JSON schema in the README page seems to attest to it.
Convenient in some ways (e.g. if you are only comfortable in JS), and does nothing useful in other contexts.
Nothing inherently wrong with it, other than it seems like a missed opportunity.
Is this more than a subset of Wordnik's Swagger?
That's hardly a relevant point or meaningful comparison. The discussion is about schema validators for TypeScript/JavaScript.
https://swagger.io/docs/specification/data-models/keywords/
This is a easier write, easier to read, compatible with JSON Schema alternative. Spartan Schema could be used instead of JSON Schema to make the document easier for humans to work with.
> Then the meta solution will become self-evident.
> Think bigger.
Are you going to share your big idea?