Most likely it's a "list" in the DSL, but implemented using Clojure's vectors, which are represented with square brackets and have convenient evaluation semanti

Most likely it's a "list" in the DSL, but implemented using Clojure's vectors, which are represented with square brackets and have convenient evaluation semantics (items are evaluated, but it's not a function call), so that it's much more common to use vectors in clojure where one would often type (list foo bar) in CL or perhaps Scheme. Often vectors are used in Clojure DSLs to differentiate from the "operator syntax" which uses actual lists. There are some exceptions in even clojure.core macros, but often you can assume that any unquoted list is evaluated as a function or macro call, even if it is a macro parameter.