diff --git a/sdk/lib/libraries.yaml b/sdk/lib/libraries.yaml
index 626222175fb..9a1a1d862a6 100644
--- a/sdk/lib/libraries.yaml
+++ b/sdk/lib/libraries.yaml
@@ -5,7 +5,7 @@
 # Note: if you edit this file, you must also generate libraries.json in this
 # directory:
 #
-#     python3 ./tools/yaml2json.py sdk/lib/libraries.yaml sdk/lib/libraries.json
+#     dart tools/yaml2json.dart sdk/lib/libraries.yaml sdk/lib/libraries.json
 #
 # We currently have several different files that needs to be updated when
 # changing libraries, sources, and patch files.  See
diff --git a/sdk/lib/vmservice_libraries.yaml b/sdk/lib/vmservice_libraries.yaml
index 40015c3f00d..d5e049c9583 100644
--- a/sdk/lib/vmservice_libraries.yaml
+++ b/sdk/lib/vmservice_libraries.yaml
@@ -5,7 +5,7 @@
 # Note: if you edit this file, you must also generate libraries.json in this
 # directory:
 #
-#     python3 ./tools/yaml2json.py sdk/lib/vmservice_libraries.yaml sdk/lib/vmservice_libraries.json
+#     dart tools/yaml2json.dart sdk/lib/vmservice_libraries.yaml sdk/lib/vmservice_libraries.json
 #
 # We currently have several different files that needs to be updated when
 # changing libraries, sources, and patch files.  See
diff --git a/tools/yaml2json.dart b/tools/yaml2json.dart
index 8ce490716b2..e8b6a07809c 100644
--- a/tools/yaml2json.dart
+++ b/tools/yaml2json.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.9
-
 import 'dart:io' show File, exit, stderr;
 
 import 'dart:isolate' show RawReceivePort;
@@ -12,7 +10,7 @@ import 'dart:convert' show JsonEncoder;
 
 import 'package:yaml/yaml.dart' show loadYaml;
 
-main(List<String> arguments) async {
+main(List<String> arguments) {
   var port = new RawReceivePort();
   if (arguments.length != 2) {
     stderr.writeln("Usage: yaml2json.dart input.yaml output.json");
@@ -20,7 +18,7 @@ main(List<String> arguments) async {
   }
   Uri input = Uri.base.resolve(arguments[0]);
   Uri output = Uri.base.resolve(arguments[1]);
-  Map yaml = loadYaml(await new File.fromUri(input).readAsString());
+  Map yaml = loadYaml(new File.fromUri(input).readAsStringSync());
   Map<String, dynamic> result = new Map<String, dynamic>();
   result["comment:0"] = "NOTE: THIS FILE IS GENERATED. DO NOT EDIT.";
   result["comment:1"] =
@@ -29,6 +27,6 @@ main(List<String> arguments) async {
     result[key] = yaml[key];
   }
   File file = new File.fromUri(output);
-  await file.writeAsString(const JsonEncoder.withIndent("  ").convert(result));
+  file.writeAsStringSync(const JsonEncoder.withIndent("  ").convert(result));
   port.close();
 }
diff --git a/tools/yaml2json.py b/tools/yaml2json.py
deleted file mode 100755
index 251f65708a4..00000000000
--- a/tools/yaml2json.py
+++ /dev/null
@@ -1,27 +0,0 @@
-#!/usr/bin/env python3
-# Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
-# for details. All rights reserved. Use of this source code is governed by a
-# BSD-style license that can be found in the LICENSE file.
-
-import os
-import subprocess
-import sys
-
-import utils
-
-
-def Main():
-    args = sys.argv[1:]
-    yaml2json_dart = os.path.relpath(
-        os.path.join(os.path.dirname(__file__), "yaml2json.dart"))
-    command = [utils.CheckedInSdkExecutable(), yaml2json_dart] + args
-
-    with utils.CoreDumpArchiver(args):
-        exit_code = subprocess.call(command)
-
-    utils.DiagnoseExitCode(exit_code, command)
-    return exit_code
-
-
-if __name__ == '__main__':
-    sys.exit(Main())