diff --git a/tools/pip-requires b/tools/pip-requires
index 822c888a..5753ce52 100644
--- a/tools/pip-requires
+++ b/tools/pip-requires
@@ -1,7 +1,7 @@
 eventlet
-msgpack-python>=0.3.0
+msgpack-python>=0.3.0  # RPC library, BGP speaker(net_cntl)
 netaddr
 oslo.config>=1.2.0
-routes
+routes  # wsgi
 six>=1.4.0
-webob>=1.2
+webob>=1.2  # wsgi