Yes, spec is a run-time tool. It's capable of multiple things, but it's mostly used at dev-time to validate fn inputs and auto-generate spec-valid data for test

Yes, spec is a run-time tool. It's capable of multiple things, but it's mostly used at dev-time to validate fn inputs and auto-generate spec-valid data for testing. It's usually disabled on production except at the edges of the system, where it frequently validates external input (e.g., making sure a JSON input conforms to an expected spec). Clojure's Schema is similar to spec, if a little different. There's also Typed Clojure, which allows you to introduce gradual typing to a Clojure code base and get compile-time static typing (though I believe it's still alpha/beta quality).