Creates and returns a map validating spec. :req and :opt are both vectors of namespaced-qualified keywords. The validator will ensure the :req keys are present. The :opt keys serve as documentation and may be used by the generator. The :req key vector supports 'and' and 'or' for key groups: (s/keys :req [::x ::y (or ::secret (and ::user ::pwd))] :opt [::z]) There are also -un versions of :req and :opt. These allow you to connect unqualified keys to specs. In each case, fully qualfied keywords are passed, which name the specs, but unqualified keys (with the same name component) are expected and checked at conform-time, and generated during gen: (s/keys :req-un [:my.ns/x :my.ns/y]) The above says keys :x and :y are required, and will be validated and generated by specs (if they exist) named :my.ns/x :my.ns/y respectively. In addition, the values of *all* namespace-qualified keys will be validated (and possibly destructured) by any registered specs. Note: there is no support for inline value specification, by design. Optionally takes :gen generator-fn, which must be a fn of no args that returns a test.check generator.