What you're talking about is effectively a type-hint. Clojure supports those like: (defn get-row-by-id [^Number id] ...) (defn get-row-by-user-name [^String s]

What you're talking about is effectively a type-hint. Clojure supports those like: (defn get-row-by-id [^Number id] ...) (defn get-row-by-user-name [^String s] ...) There's also destructuring which both "extracts" local variables from data structures and serves as an informal documentation/description of the data shape. You can combine type-hints and destructuring for a very powerful effect. Nowadays, I almost never have a problem "remembering" what or what shape of data I need to pass around.