diff --git a/pkg/onionkey/key.go b/pkg/onionkey/key.go
index 895edae..b91d43a 100644
--- a/pkg/onionkey/key.go
+++ b/pkg/onionkey/key.go
@@ -1,3 +1,5 @@
+// Package onionkey manages onion service key generation, serialization, and
+// service ID calculation. Currently only supports version 3 onions.
 package onionkey
 
 import (