diff --git a/doc/plugins/exports.js b/doc/plugins/exports.js
index 8e483e3c59..90b202de2a 100644
--- a/doc/plugins/exports.js
+++ b/doc/plugins/exports.js
@@ -1,3 +1,9 @@
+/*
+ * This plugin parses goog.exportSymbol and goog.exportProperty calls to build
+ * a list of API symbols and properties. Everything else is marked undocumented,
+ * which will remove it from the docs.
+ */
+
 var api = [];
 
 function collectExports(source) {