diff --git a/cluster/local/util.sh b/cluster/local/util.sh
index 73eab5ed869..da262fdf249 100755
--- a/cluster/local/util.sh
+++ b/cluster/local/util.sh
@@ -18,6 +18,13 @@ function prepare-e2e() {
   echo "Local doesn't need special preparations for e2e tests" 1>&2
 }
 
+# Detect the IP for the master
+#
+# Vars set:
+#   KUBE_MASTER
+#   KUBE_MASTER_IP
+# Vars exported:
+#   KUBE_MASTER_URL
 function detect-master {
   KUBE_MASTER=localhost
   KUBE_MASTER_IP=127.0.0.1