diff --git a/bazel/workspace_defs.bzl b/bazel/workspace_defs.bzl
index 9abaa2f2a8..1706d61fe3 100644
--- a/bazel/workspace_defs.bzl
+++ b/bazel/workspace_defs.bzl
@@ -1,3 +1,29 @@
+# Copyright (c) 2009-2021, Google LLC
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above copyright
+#       notice, this list of conditions and the following disclaimer in the
+#       documentation and/or other materials provided with the distribution.
+#     * Neither the name of Google LLC nor the
+#       names of its contributors may be used to endorse or promote products
+#       derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL Google LLC BE LIABLE FOR ANY
+# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Repository rule for using Python 3.x headers from the system."""
 
 _build_file = """
 cc_library(
@@ -21,7 +47,23 @@ def _python_headers_impl(repository_ctx):
   repository_ctx.symlink(path, "python")
   repository_ctx.file("BUILD.bazel", _build_file)
 
-
+# The python_headers() repository rule exposes Python headers from the system.
+#
+# In WORKSPACE:
+#   python_headers(
+#       name = "python_headers_repo",
+#   )
+#
+# This repository exposes a single rule that you can depend on from BUILD:
+#   cc_library(
+#     name = "foobar",
+#     srcs = ["foobar.cc"],
+#     deps = ["@python_headers_repo//:python_headers"],
+#   )
+#
+# The headers will be from any version of Python >=3.6.  This is intended for
+# use with the Python "limited API," which only exposes symbols that are ABI
+# compatible from version to version.
 python_headers = repository_rule(
     implementation = _python_headers_impl,
     local = True,
diff --git a/cmake/make_cmakelists.py b/cmake/make_cmakelists.py
index 33d8d85639..b3266fa18b 100755
--- a/cmake/make_cmakelists.py
+++ b/cmake/make_cmakelists.py
@@ -220,6 +220,9 @@ class WorkspaceFileFunctions(object):
   def rules_fuzzing_init(self):
     pass
 
+  def python_headers(self, **kwargs):
+    pass
+
 
 class Converter(object):
   def __init__(self):