diff --git a/src/cljck/io.clj b/src/cljck/io.clj
index 60b9bf5..3ef56a6 100644
--- a/src/cljck/io.clj
+++ b/src/cljck/io.clj
@@ -1,6 +1,7 @@
 (ns cljck.io
   (:gen-class)
   (:require
+   [cljck.utils :refer [multi-functions]]
    [cljck.io
     [keyboard :refer [press]]
     [mouse :refer [click move-to mouse-pointer scroll-down scroll-up]]]
@@ -20,58 +21,68 @@
 
   The argument is expected to be a vector like [:move-to 100 100] or [:click].
   Dispatches on first."
-  first)
-
-(defmethod process-event :click
+  (comp name first))
+
+(defmethod process-event :default
+  [exp]
+  (throw (IllegalArgumentException.
+          (with-out-str
+            (println "The following expression wasn't recognized:")
+            (clojure.pprint/pprint exp)
+            (println "No such command:" (first exp))
+            (println "Valid commands:" (multi-functions process-event))
+            (println "Check the API in the README for help.")))))
+
+(defmethod process-event "click"
   [_]
   (click :left))
 
-(defmethod process-event :if
+(defmethod process-event "if"
   [[_ condition then else]]
   (if (process-event condition)
     (process-event then)
     (process-event else)))
 
-(defmethod process-event :move-to
+(defmethod process-event "move-to"
   [[_ x y]]
   (move-to x y))
 
-(defmethod process-event :pointer-near
+(defmethod process-event "pointer-near"
   [[_ x y distance]]
   (let [[mouse-x mouse-y] (mouse-pointer)]
     (and (< (- x distance) mouse-x (+ x distance))
          (< (- y distance) mouse-y (+ y distance)))))
 
-(defmethod process-event :press
+(defmethod process-event "press"
   [[_ key-string]]
   (press key-string))
 
-(defmethod process-event :repeat
+(defmethod process-event "repeat"
   [[_ n & commands]]
   (dotimes [_ n]
     (doseq [command commands]
       (process-event command))))
 
-(defmethod process-event :repeatedly
+(defmethod process-event "repeatedly"
   [[_ & commands]]
   (loop []
     (doseq [command commands]
       (process-event command))
     (recur)))
 
-(defmethod process-event :scroll-down
+(defmethod process-event "scroll-down"
   [[_ & amount]]
   (apply scroll-down amount))
 
-(defmethod process-event :scroll-up
+(defmethod process-event "scroll-up"
   [[_ & amount]]
   (apply scroll-up amount))
 
-(defmethod process-event :wait
+(defmethod process-event "wait"
   [[_ miliseconds]]
   (<!! (timeout miliseconds)))
 
-(defmethod process-event :when
+(defmethod process-event "when"
   [[_ condition & body]]
   (when (process-event condition)
     (apply process-event body)))
diff --git a/src/cljck/utils.clj b/src/cljck/utils.clj
new file mode 100644
index 0000000..16277cd
--- /dev/null
+++ b/src/cljck/utils.clj
@@ -0,0 +1,10 @@
+(ns cljck.utils)
+
+(defn multi-functions
+  "Returns a sorted list of the functions contained in the multimethod."
+  [multimethod]
+  (->> multimethod
+       (.getMethodTable)
+       (map first)
+       (remove (partial = :default))
+       (sort)))