diff --git a/group_vars/all.yml b/group_vars/all.yml
index 691e7d0..61c14e7 100644
--- a/group_vars/all.yml
+++ b/group_vars/all.yml
@@ -1,4 +1,10 @@
 ---
+
+# This file is the place for cross-role defaults for all products, and
+# common parameters from the infrastructure-deployment phase of the
+# build (e.g. CloudFormation). More specific vars should go in
+# <role>/defaults/main.yml or in the various playbooks.
+
 java_version: "1.8.0"
 postgres_version: "9.6"
 git_version: "2.14.4"