diff --git a/schema.graphqls b/schema.graphqls
index 4e3c22d..a2a8eca 100644
--- a/schema.graphqls
+++ b/schema.graphqls
@@ -1,3 +1,6 @@
+# The Interchange system schema.
+# Note how Passio ID and parking ID are abstracted away
+# from the endpoints.
 type System {
   id: ID!
   name: String!