diff --git a/tools/interop_matrix/run_interop_matrix_tests.py b/tools/interop_matrix/run_interop_matrix_tests.py
index 3f92c8e6641..120ba08b465 100755
--- a/tools/interop_matrix/run_interop_matrix_tests.py
+++ b/tools/interop_matrix/run_interop_matrix_tests.py
@@ -86,6 +86,8 @@ argp.add_argument(
     type=str,
     nargs='?',
     help='Upload test results to a specified BQ table.')
+# Requests will be routed through specified VIP by default.
+# See go/grpc-interop-tests (internal-only) for details.
 argp.add_argument(
     '--server_host',
     default='74.125.206.210',
diff --git a/tools/run_tests/run_interop_tests.py b/tools/run_tests/run_interop_tests.py
index cc6901bdebe..108f91e8383 100755
--- a/tools/run_tests/run_interop_tests.py
+++ b/tools/run_tests/run_interop_tests.py
@@ -1152,7 +1152,8 @@ def aggregate_http2_results(stdout):
     }
 
 
-# A dictionary of prod servers to test.
+# A dictionary of prod servers to test against.
+# See go/grpc-interop-tests (internal-only) for details.
 prod_servers = {
     'default': 'grpc-test.sandbox.googleapis.com',
     'gateway_v4': 'grpc-test4.sandbox.googleapis.com',