diff --git a/index.bzl b/index.bzl
index 5178b8ba4c..e0078cc901 100644
--- a/index.bzl
+++ b/index.bzl
@@ -3,6 +3,13 @@
 # Use of this source code is governed by an MIT-style license that can be
 # found in the LICENSE file at https://angular.io/license
 """ Public API surface is re-exported here.
+
+This API is exported for user's building angular from source in downstream
+projects. The rules from packages/bazel are re-exported here as well
+as the ng_setup_workspace repository rule needed when building angular
+from source downstream. Alternately, this API is available from the
+@angular/bazel npm package if the npm distribution of angular is
+used in a downstream project.
 """
 
 load("//packages/bazel:index.bzl",