diff --git a/lib/md_tools.sh b/lib/md_tools.sh
index 9b90219..0b5fa9b 100755
--- a/lib/md_tools.sh
+++ b/lib/md_tools.sh
@@ -120,6 +120,12 @@ getEntityFromServer () {
 		return 2
 	fi
 	
+	# external dependency
+	if [ "$(type -t percent_encode)" != function ]; then
+		echo "ERROR: $FUNCNAME: function percent_encode not found" >&2
+		return 2
+	fi
+
 	local tmp_dir
 	local mdq_base_url
 	local tmp_response_file
@@ -177,11 +183,11 @@ getEntityFromServer () {
 	fi
 	entityID=$1
 
-	# URL-encode the identifier
-	encoded_id=$( urlencode $entityID )
+	# percent-encode the identifier
+	encoded_id=$( percent_encode $entityID )
 	return_status=$?
 	if [ "$return_status" -ne 0 ]; then
-		echo "ERROR: $FUNCNAME: failed to URL-encode the entityID: $entityID" >&2
+		echo "ERROR: $FUNCNAME: failed to percent-encode the entityID: $entityID" >&2
 		return 3
 	fi
 
@@ -222,10 +228,11 @@ getEntityFromServer () {
 # Construct a request URL per the MDQ Protocol specification.
 # See: https://github.com/iay/md-query
 #
-# Usage: construct_mdq_url <base_url> <url_encoded_id>
+# Usage: construct_mdq_url <base_url> <percent_encoded_id>
 #
 # To construct a reference to ALL entities served by the 
-# metadata query server, simply omit the second argument
+# metadata query server, simply omit the second argument.
+# (Note: Not all MDQ servers serve such an aggregate.)
 #######################################################################
 construct_mdq_url () {
 
@@ -251,6 +258,8 @@ construct_mdq_url () {
 }
 
 #######################################################################
+# This function is DEPRECATED. Use percent_encode instead.
+#
 # URL-encode an arbitrary string.
 # See: https://gist.github.com/cdown/1163649
 #