diff --git a/pkgs/json_syntax_generator/lib/src/generator/helper_library.dart b/pkgs/json_syntax_generator/lib/src/generator/helper_library.dart
new file mode 100644
index 0000000000..8703d13764
--- /dev/null
+++ b/pkgs/json_syntax_generator/lib/src/generator/helper_library.dart
@@ -0,0 +1,112 @@
+// Copyright (c) 2025, 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.
+
+/// Helper methods for the code generator that are added to the generated file.
+///
+/// This simplifies the code generator.
+const helperLib = r'''
+extension on Map<String, Object?> {
+  T get<T extends Object?>(String key) {
+    final value = this[key];
+    if (value is T) return value;
+    if (value == null) {
+      throw FormatException('No value was provided for required key: $key');
+    }
+    throw FormatException(
+      'Unexpected value \'$value\' for key \'.$key\'. '
+      'Expected a $T.',
+    );
+  }
+
+  List<T> list<T extends Object?>(String key) =>
+      _castList<T>(get<List<Object?>>(key), key);
+
+  List<T>? optionalList<T extends Object?>(String key) =>
+      switch (get<List<Object?>?>(key)?.cast<T>()) {
+        null => null,
+        final l => _castList<T>(l, key),
+      };
+
+  /// [List.cast] but with [FormatException]s.
+  static List<T> _castList<T extends Object?>(List<Object?> list, String key) {
+    for (final value in list) {
+      if (value is! T) {
+        throw FormatException(
+          'Unexpected value \'$list\' (${list.runtimeType}) for key \'.$key\'. '
+          'Expected a ${List<T>}.',
+        );
+      }
+    }
+    return list.cast();
+  }
+
+  Map<String, T> map$<T extends Object?>(String key) =>
+      _castMap<T>(get<Map<String, Object?>>(key), key);
+
+  Map<String, T>? optionalMap<T extends Object?>(String key) =>
+      switch (get<Map<String, Object?>?>(key)) {
+        null => null,
+        final m => _castMap<T>(m, key),
+      };
+
+  /// [Map.cast] but with [FormatException]s.
+  static Map<String, T> _castMap<T extends Object?>(
+    Map<String, Object?> map_,
+    String key,
+  ) {
+    for (final value in map_.values) {
+      if (value is! T) {
+        throw FormatException(
+          'Unexpected value \'$map_\' (${map_.runtimeType}) for key \'.$key\'.'
+          'Expected a ${Map<String, T>}.',
+        );
+      }
+    }
+    return map_.cast();
+  }
+
+  List<String>? optionalStringList(String key) => optionalList<String>(key);
+
+  List<String> stringList(String key) => list<String>(key);
+
+  Uri path(String key) => _fileSystemPathToUri(get<String>(key));
+
+  Uri? optionalPath(String key) {
+    final value = get<String?>(key);
+    if (value == null) return null;
+    return _fileSystemPathToUri(value);
+  }
+
+  List<Uri>? optionalPathList(String key) {
+    final strings = optionalStringList(key);
+    if (strings == null) {
+      return null;
+    }
+    return [for (final string in strings) _fileSystemPathToUri(string)];
+  }
+
+  static Uri _fileSystemPathToUri(String path) {
+    if (path.endsWith(Platform.pathSeparator)) {
+      return Uri.directory(path);
+    }
+    return Uri.file(path);
+  }
+}
+
+extension on List<Uri> {
+  List<String> toJson() => [for (final uri in this) uri.toFilePath()];
+}
+
+extension <K extends Comparable<K>, V extends Object?> on Map<K, V> {
+  void sortOnKey() {
+    final result = <K, V>{};
+    final keysSorted = keys.toList()..sort();
+    for (final key in keysSorted) {
+      result[key] = this[key] as V;
+    }
+    clear();
+    addAll(result);
+  }
+}
+''';
diff --git a/pkgs/json_syntax_generator/lib/src/generator/syntax_generator.dart b/pkgs/json_syntax_generator/lib/src/generator/syntax_generator.dart
index 1ee2e774cd..2873f6e4f4 100644
--- a/pkgs/json_syntax_generator/lib/src/generator/syntax_generator.dart
+++ b/pkgs/json_syntax_generator/lib/src/generator/syntax_generator.dart
@@ -6,6 +6,7 @@ import '../model/class_info.dart';
 import '../model/dart_type.dart';
 import '../model/property_info.dart';
 import '../model/schema_info.dart';
+import 'helper_library.dart';
 
 /// Generates Dart code from a [SchemaInfo].
 ///
@@ -35,13 +36,17 @@ class SyntaxGenerator {
 
 // This file is generated, do not edit.
 
-import '../utils/json.dart';
+// ignore_for_file: unused_element
+
+import 'dart:io';
 ''');
 
     for (final classInfo in schemaInfo.classes) {
       buffer.writeln(_generateClass(classInfo));
     }
 
+    buffer.writeln(helperLib);
+
     return buffer.toString();
   }
 
@@ -301,7 +306,7 @@ class $className {
       case EnumClassInfo():
         if (required) {
           buffer.writeln('''
-$dartType get $fieldName => $classType.fromJson( json.string('$jsonKey') );
+$dartType get $fieldName => $classType.fromJson( json.get<String>('$jsonKey') );
 ''');
           if (!property.isOverride) {
             buffer.writeln('''
@@ -313,7 +318,7 @@ set $setterName($dartType value) {
         } else {
           buffer.writeln('''
 $dartType get $fieldName {
-  final string = json.optionalString('$jsonKey');
+  final string = json.get<String?>('$jsonKey');
   if(string == null) return null;
   return $classType.fromJson(string);
 }
@@ -384,7 +389,7 @@ set $setterName($dartType value) {
       case 'String':
         if (required) {
           buffer.writeln('''
-String get $fieldName => json.string('$jsonKey');
+String get $fieldName => json.get<String>('$jsonKey');
 
 set $setterName(String value) {
   json['$jsonKey'] = value;
@@ -393,7 +398,7 @@ set $setterName(String value) {
 ''');
         } else {
           buffer.writeln('''
-String? get $fieldName => json.optionalString('$jsonKey');
+String? get $fieldName => json.get<String?>('$jsonKey');
 
 set $setterName(String? value) {
   if (value == null) {
@@ -415,7 +420,7 @@ set $setterName(int value) => json['$jsonKey'] = value;
 ''');
         } else {
           buffer.writeln('''
-int? get $fieldName => json.getOptional<int>('$jsonKey');
+int? get $fieldName => json.get<int?>('$jsonKey');
 
 set $setterName(int? value) {
   if (value == null) {
@@ -440,7 +445,7 @@ set $setterName(bool value) {
 ''');
         } else {
           buffer.writeln('''
-bool? get $fieldName => json.getOptional<bool>('$jsonKey');
+bool? get $fieldName => json.get<bool?>('$jsonKey');
 
 set $setterName(bool? value) {
   if (value == null) {
diff --git a/pkgs/native_assets_cli/lib/src/code_assets/syntax.g.dart b/pkgs/native_assets_cli/lib/src/code_assets/syntax.g.dart
index e515eac434..bcdcd325d7 100644
--- a/pkgs/native_assets_cli/lib/src/code_assets/syntax.g.dart
+++ b/pkgs/native_assets_cli/lib/src/code_assets/syntax.g.dart
@@ -4,7 +4,9 @@
 
 // This file is generated, do not edit.
 
-import '../utils/json.dart';
+// ignore_for_file: unused_element
+
+import 'dart:io';
 
 class AndroidCodeConfig {
   final Map<String, Object?> json;
@@ -16,7 +18,7 @@ class AndroidCodeConfig {
     json.sortOnKey();
   }
 
-  int? get targetNdkApi => json.getOptional<int>('target_ndk_api');
+  int? get targetNdkApi => json.get<int?>('target_ndk_api');
 
   set _targetNdkApi(int? value) {
     if (value == null) {
@@ -86,7 +88,7 @@ class Asset {
     json.sortOnKey();
   }
 
-  String? get type => json.optionalString('type');
+  String? get type => json.get<String?>('type');
 
   set _type(String? value) {
     if (value == null) {
@@ -136,7 +138,7 @@ class NativeCodeAsset extends Asset {
   }
 
   Architecture? get architecture {
-    final string = json.optionalString('architecture');
+    final string = json.get<String?>('architecture');
     if (string == null) return null;
     return Architecture.fromJson(string);
   }
@@ -159,7 +161,7 @@ class NativeCodeAsset extends Asset {
     }
   }
 
-  String get id => json.string('id');
+  String get id => json.get<String>('id');
 
   set _id(String value) {
     json['id'] = value;
@@ -169,7 +171,7 @@ class NativeCodeAsset extends Asset {
 
   set _linkMode(LinkMode value) => json['link_mode'] = value.json;
 
-  OS get os => OS.fromJson(json.string('os'));
+  OS get os => OS.fromJson(json.get<String>('os'));
 
   set _os(OS value) {
     json['os'] = value.name;
@@ -397,7 +399,7 @@ class CodeConfig {
   }
 
   LinkModePreference get linkModePreference =>
-      LinkModePreference.fromJson(json.string('link_mode_preference'));
+      LinkModePreference.fromJson(json.get<String>('link_mode_preference'));
 
   set _linkModePreference(LinkModePreference value) {
     json['link_mode_preference'] = value.name;
@@ -420,13 +422,13 @@ class CodeConfig {
   }
 
   Architecture get targetArchitecture =>
-      Architecture.fromJson(json.string('target_architecture'));
+      Architecture.fromJson(json.get<String>('target_architecture'));
 
   set _targetArchitecture(Architecture value) {
     json['target_architecture'] = value.name;
   }
 
-  OS get targetOs => OS.fromJson(json.string('target_os'));
+  OS get targetOs => OS.fromJson(json.get<String>('target_os'));
 
   set _targetOs(OS value) {
     json['target_os'] = value.name;
@@ -478,7 +480,7 @@ class IOSCodeConfig {
     json.sortOnKey();
   }
 
-  String? get targetSdk => json.optionalString('target_sdk');
+  String? get targetSdk => json.get<String?>('target_sdk');
 
   set _targetSdk(String? value) {
     if (value == null) {
@@ -488,7 +490,7 @@ class IOSCodeConfig {
     }
   }
 
-  int? get targetVersion => json.getOptional<int>('target_version');
+  int? get targetVersion => json.get<int?>('target_version');
 
   set _targetVersion(int? value) {
     if (value == null) {
@@ -512,7 +514,7 @@ class LinkMode {
     json.sortOnKey();
   }
 
-  String get type => json.string('type');
+  String get type => json.get<String>('type');
 
   set _type(String value) {
     json['type'] = value;
@@ -670,7 +672,7 @@ class MacOSCodeConfig {
     json.sortOnKey();
   }
 
-  int? get targetVersion => json.getOptional<int>('target_version');
+  int? get targetVersion => json.get<int?>('target_version');
 
   set _targetVersion(int? value) {
     if (value == null) {
@@ -720,3 +722,107 @@ class OS {
   @override
   String toString() => name;
 }
+
+extension on Map<String, Object?> {
+  T get<T extends Object?>(String key) {
+    final value = this[key];
+    if (value is T) return value;
+    if (value == null) {
+      throw FormatException('No value was provided for required key: $key');
+    }
+    throw FormatException(
+      'Unexpected value \'$value\' for key \'.$key\'. '
+      'Expected a $T.',
+    );
+  }
+
+  List<T> list<T extends Object?>(String key) =>
+      _castList<T>(get<List<Object?>>(key), key);
+
+  List<T>? optionalList<T extends Object?>(String key) =>
+      switch (get<List<Object?>?>(key)?.cast<T>()) {
+        null => null,
+        final l => _castList<T>(l, key),
+      };
+
+  /// [List.cast] but with [FormatException]s.
+  static List<T> _castList<T extends Object?>(List<Object?> list, String key) {
+    for (final value in list) {
+      if (value is! T) {
+        throw FormatException(
+          'Unexpected value \'$list\' (${list.runtimeType}) for key \'.$key\'. '
+          'Expected a ${List<T>}.',
+        );
+      }
+    }
+    return list.cast();
+  }
+
+  Map<String, T> map$<T extends Object?>(String key) =>
+      _castMap<T>(get<Map<String, Object?>>(key), key);
+
+  Map<String, T>? optionalMap<T extends Object?>(String key) =>
+      switch (get<Map<String, Object?>?>(key)) {
+        null => null,
+        final m => _castMap<T>(m, key),
+      };
+
+  /// [Map.cast] but with [FormatException]s.
+  static Map<String, T> _castMap<T extends Object?>(
+    Map<String, Object?> map_,
+    String key,
+  ) {
+    for (final value in map_.values) {
+      if (value is! T) {
+        throw FormatException(
+          'Unexpected value \'$map_\' (${map_.runtimeType}) for key \'.$key\'.'
+          'Expected a ${Map<String, T>}.',
+        );
+      }
+    }
+    return map_.cast();
+  }
+
+  List<String>? optionalStringList(String key) => optionalList<String>(key);
+
+  List<String> stringList(String key) => list<String>(key);
+
+  Uri path(String key) => _fileSystemPathToUri(get<String>(key));
+
+  Uri? optionalPath(String key) {
+    final value = get<String?>(key);
+    if (value == null) return null;
+    return _fileSystemPathToUri(value);
+  }
+
+  List<Uri>? optionalPathList(String key) {
+    final strings = optionalStringList(key);
+    if (strings == null) {
+      return null;
+    }
+    return [for (final string in strings) _fileSystemPathToUri(string)];
+  }
+
+  static Uri _fileSystemPathToUri(String path) {
+    if (path.endsWith(Platform.pathSeparator)) {
+      return Uri.directory(path);
+    }
+    return Uri.file(path);
+  }
+}
+
+extension on List<Uri> {
+  List<String> toJson() => [for (final uri in this) uri.toFilePath()];
+}
+
+extension<K extends Comparable<K>, V extends Object?> on Map<K, V> {
+  void sortOnKey() {
+    final result = <K, V>{};
+    final keysSorted = keys.toList()..sort();
+    for (final key in keysSorted) {
+      result[key] = this[key] as V;
+    }
+    clear();
+    addAll(result);
+  }
+}
diff --git a/pkgs/native_assets_cli/lib/src/config.dart b/pkgs/native_assets_cli/lib/src/config.dart
index f764f5c93d..a285ab2147 100644
--- a/pkgs/native_assets_cli/lib/src/config.dart
+++ b/pkgs/native_assets_cli/lib/src/config.dart
@@ -130,7 +130,7 @@ sealed class HookInputBuilder {
 final class BuildInput extends HookInput {
   Map<String, Metadata> get metadata => {
     for (final entry in (_syntaxBuildInput.dependencyMetadata ?? {}).entries)
-      entry.key: Metadata.fromJson(as<Map<String, Object?>>(entry.value)),
+      entry.key: Metadata.fromJson(entry.value),
   };
 
   @override
diff --git a/pkgs/native_assets_cli/lib/src/data_assets/syntax.g.dart b/pkgs/native_assets_cli/lib/src/data_assets/syntax.g.dart
index 8a87071ccd..592092901d 100644
--- a/pkgs/native_assets_cli/lib/src/data_assets/syntax.g.dart
+++ b/pkgs/native_assets_cli/lib/src/data_assets/syntax.g.dart
@@ -4,7 +4,9 @@
 
 // This file is generated, do not edit.
 
-import '../utils/json.dart';
+// ignore_for_file: unused_element
+
+import 'dart:io';
 
 class Asset {
   final Map<String, Object?> json;
@@ -16,7 +18,7 @@ class Asset {
     json.sortOnKey();
   }
 
-  String? get type => json.optionalString('type');
+  String? get type => json.get<String?>('type');
 
   set _type(String? value) {
     if (value == null) {
@@ -60,13 +62,13 @@ class DataAsset extends Asset {
     json['file'] = value.toFilePath();
   }
 
-  String get name => json.string('name');
+  String get name => json.get<String>('name');
 
   set _name(String value) {
     json['name'] = value;
   }
 
-  String get package => json.string('package');
+  String get package => json.get<String>('package');
 
   set _package(String value) {
     json['package'] = value;
@@ -81,3 +83,107 @@ extension DataAssetExtension on Asset {
 
   DataAsset get asDataAsset => DataAsset.fromJson(json);
 }
+
+extension on Map<String, Object?> {
+  T get<T extends Object?>(String key) {
+    final value = this[key];
+    if (value is T) return value;
+    if (value == null) {
+      throw FormatException('No value was provided for required key: $key');
+    }
+    throw FormatException(
+      'Unexpected value \'$value\' for key \'.$key\'. '
+      'Expected a $T.',
+    );
+  }
+
+  List<T> list<T extends Object?>(String key) =>
+      _castList<T>(get<List<Object?>>(key), key);
+
+  List<T>? optionalList<T extends Object?>(String key) =>
+      switch (get<List<Object?>?>(key)?.cast<T>()) {
+        null => null,
+        final l => _castList<T>(l, key),
+      };
+
+  /// [List.cast] but with [FormatException]s.
+  static List<T> _castList<T extends Object?>(List<Object?> list, String key) {
+    for (final value in list) {
+      if (value is! T) {
+        throw FormatException(
+          'Unexpected value \'$list\' (${list.runtimeType}) for key \'.$key\'. '
+          'Expected a ${List<T>}.',
+        );
+      }
+    }
+    return list.cast();
+  }
+
+  Map<String, T> map$<T extends Object?>(String key) =>
+      _castMap<T>(get<Map<String, Object?>>(key), key);
+
+  Map<String, T>? optionalMap<T extends Object?>(String key) =>
+      switch (get<Map<String, Object?>?>(key)) {
+        null => null,
+        final m => _castMap<T>(m, key),
+      };
+
+  /// [Map.cast] but with [FormatException]s.
+  static Map<String, T> _castMap<T extends Object?>(
+    Map<String, Object?> map_,
+    String key,
+  ) {
+    for (final value in map_.values) {
+      if (value is! T) {
+        throw FormatException(
+          'Unexpected value \'$map_\' (${map_.runtimeType}) for key \'.$key\'.'
+          'Expected a ${Map<String, T>}.',
+        );
+      }
+    }
+    return map_.cast();
+  }
+
+  List<String>? optionalStringList(String key) => optionalList<String>(key);
+
+  List<String> stringList(String key) => list<String>(key);
+
+  Uri path(String key) => _fileSystemPathToUri(get<String>(key));
+
+  Uri? optionalPath(String key) {
+    final value = get<String?>(key);
+    if (value == null) return null;
+    return _fileSystemPathToUri(value);
+  }
+
+  List<Uri>? optionalPathList(String key) {
+    final strings = optionalStringList(key);
+    if (strings == null) {
+      return null;
+    }
+    return [for (final string in strings) _fileSystemPathToUri(string)];
+  }
+
+  static Uri _fileSystemPathToUri(String path) {
+    if (path.endsWith(Platform.pathSeparator)) {
+      return Uri.directory(path);
+    }
+    return Uri.file(path);
+  }
+}
+
+extension on List<Uri> {
+  List<String> toJson() => [for (final uri in this) uri.toFilePath()];
+}
+
+extension<K extends Comparable<K>, V extends Object?> on Map<K, V> {
+  void sortOnKey() {
+    final result = <K, V>{};
+    final keysSorted = keys.toList()..sort();
+    for (final key in keysSorted) {
+      result[key] = this[key] as V;
+    }
+    clear();
+    addAll(result);
+  }
+}
diff --git a/pkgs/native_assets_cli/lib/src/encoded_asset.dart b/pkgs/native_assets_cli/lib/src/encoded_asset.dart
index 46a8fc33a1..959f3a6f08 100644
--- a/pkgs/native_assets_cli/lib/src/encoded_asset.dart
+++ b/pkgs/native_assets_cli/lib/src/encoded_asset.dart
@@ -4,6 +4,7 @@
 
 import 'package:collection/collection.dart';
 
+import 'hook/syntax.g.dart' as syntax;
 import 'utils/json.dart';
 
 /// An encoding of a particular asset type.
@@ -17,11 +18,13 @@ final class EncodedAsset {
   EncodedAsset(this.type, this.encoding);
 
   /// Decode an [EncodedAsset] from json.
-  factory EncodedAsset.fromJson(Map<String, Object?> json) =>
-      EncodedAsset(json.get<String>(_typeKey), {
-        for (final key in json.keys)
-          if (key != _typeKey) key: json[key],
-      });
+  factory EncodedAsset.fromJson(Map<String, Object?> json) {
+    final syntax_ = syntax.Asset.fromJson(json);
+    return EncodedAsset(syntax_.type, {
+      for (final key in json.keys)
+        if (key != _typeKey) key: json[key],
+    });
+  }
 
   /// Encode this [EncodedAsset] tojson.
   Map<String, Object?> toJson() =>
diff --git a/pkgs/native_assets_cli/lib/src/hook/syntax.g.dart b/pkgs/native_assets_cli/lib/src/hook/syntax.g.dart
index 5bd62885da..5accc92283 100644
--- a/pkgs/native_assets_cli/lib/src/hook/syntax.g.dart
+++ b/pkgs/native_assets_cli/lib/src/hook/syntax.g.dart
@@ -4,7 +4,9 @@
 
 // This file is generated, do not edit.
 
-import '../utils/json.dart';
+// ignore_for_file: unused_element
+
+import 'dart:io';
 
 class Asset {
   final Map<String, Object?> json;
@@ -16,7 +18,7 @@ class Asset {
     json.sortOnKey();
   }
 
-  String get type => json.string('type');
+  String get type => json.get<String>('type');
 
   set _type(String value) {
     json['type'] = value;
@@ -236,7 +238,7 @@ class HookInput {
     json.sortOnKey();
   }
 
-  String get packageName => json.string('package_name');
+  String get packageName => json.get<String>('package_name');
 
   set packageName(String value) {
     json['package_name'] = value;
@@ -250,7 +252,7 @@ class HookInput {
     json.sortOnKey();
   }
 
-  String get version => json.string('version');
+  String get version => json.get<String>('version');
 
   set version(String value) {
     json['version'] = value;
@@ -311,14 +313,14 @@ class HookOutput {
     json.sortOnKey();
   }
 
-  String get timestamp => json.string('timestamp');
+  String get timestamp => json.get<String>('timestamp');
 
   set timestamp(String value) {
     json['timestamp'] = value;
     json.sortOnKey();
   }
 
-  String get version => json.string('version');
+  String get version => json.get<String>('version');
 
   set version(String value) {
     json['version'] = value;
@@ -403,3 +405,107 @@ class LinkOutput extends HookOutput {
   @override
   String toString() => 'LinkOutput($json)';
 }
+
+extension on Map<String, Object?> {
+  T get<T extends Object?>(String key) {
+    final value = this[key];
+    if (value is T) return value;
+    if (value == null) {
+      throw FormatException('No value was provided for required key: $key');
+    }
+    throw FormatException(
+      'Unexpected value \'$value\' for key \'.$key\'. '
+      'Expected a $T.',
+    );
+  }
+
+  List<T> list<T extends Object?>(String key) =>
+      _castList<T>(get<List<Object?>>(key), key);
+
+  List<T>? optionalList<T extends Object?>(String key) =>
+      switch (get<List<Object?>?>(key)?.cast<T>()) {
+        null => null,
+        final l => _castList<T>(l, key),
+      };
+
+  /// [List.cast] but with [FormatException]s.
+  static List<T> _castList<T extends Object?>(List<Object?> list, String key) {
+    for (final value in list) {
+      if (value is! T) {
+        throw FormatException(
+          'Unexpected value \'$list\' (${list.runtimeType}) for key \'.$key\'. '
+          'Expected a ${List<T>}.',
+        );
+      }
+    }
+    return list.cast();
+  }
+
+  Map<String, T> map$<T extends Object?>(String key) =>
+      _castMap<T>(get<Map<String, Object?>>(key), key);
+
+  Map<String, T>? optionalMap<T extends Object?>(String key) =>
+      switch (get<Map<String, Object?>?>(key)) {
+        null => null,
+        final m => _castMap<T>(m, key),
+      };
+
+  /// [Map.cast] but with [FormatException]s.
+  static Map<String, T> _castMap<T extends Object?>(
+    Map<String, Object?> map_,
+    String key,
+  ) {
+    for (final value in map_.values) {
+      if (value is! T) {
+        throw FormatException(
+          'Unexpected value \'$map_\' (${map_.runtimeType}) for key \'.$key\'.'
+          'Expected a ${Map<String, T>}.',
+        );
+      }
+    }
+    return map_.cast();
+  }
+
+  List<String>? optionalStringList(String key) => optionalList<String>(key);
+
+  List<String> stringList(String key) => list<String>(key);
+
+  Uri path(String key) => _fileSystemPathToUri(get<String>(key));
+
+  Uri? optionalPath(String key) {
+    final value = get<String?>(key);
+    if (value == null) return null;
+    return _fileSystemPathToUri(value);
+  }
+
+  List<Uri>? optionalPathList(String key) {
+    final strings = optionalStringList(key);
+    if (strings == null) {
+      return null;
+    }
+    return [for (final string in strings) _fileSystemPathToUri(string)];
+  }
+
+  static Uri _fileSystemPathToUri(String path) {
+    if (path.endsWith(Platform.pathSeparator)) {
+      return Uri.directory(path);
+    }
+    return Uri.file(path);
+  }
+}
+
+extension on List<Uri> {
+  List<String> toJson() => [for (final uri in this) uri.toFilePath()];
+}
+
+extension<K extends Comparable<K>, V extends Object?> on Map<K, V> {
+  void sortOnKey() {
+    final result = <K, V>{};
+    final keysSorted = keys.toList()..sort();
+    for (final key in keysSorted) {
+      result[key] = this[key] as V;
+    }
+    clear();
+    addAll(result);
+  }
+}
diff --git a/pkgs/native_assets_cli/lib/src/metadata.dart b/pkgs/native_assets_cli/lib/src/metadata.dart
index c02e85deca..c3bd3c56a3 100644
--- a/pkgs/native_assets_cli/lib/src/metadata.dart
+++ b/pkgs/native_assets_cli/lib/src/metadata.dart
@@ -4,15 +4,13 @@
 
 import 'package:collection/collection.dart';
 
-import 'utils/json.dart';
-
 class Metadata {
   final Map<String, Object?> metadata;
 
   const Metadata(this.metadata);
 
-  factory Metadata.fromJson(Map<Object?, Object?>? jsonMap) =>
-      Metadata(jsonMap?.formatCast<String, Object>() ?? {});
+  factory Metadata.fromJson(Map<String, Object?>? jsonMap) =>
+      Metadata(jsonMap ?? {});
 
   Map<String, Object?> toJson() => metadata;
 
diff --git a/pkgs/native_assets_cli/lib/src/model/dependencies.dart b/pkgs/native_assets_cli/lib/src/model/dependencies.dart
index 79920ae3d9..369b6d2b62 100644
--- a/pkgs/native_assets_cli/lib/src/model/dependencies.dart
+++ b/pkgs/native_assets_cli/lib/src/model/dependencies.dart
@@ -7,7 +7,6 @@ import 'dart:convert';
 import 'package:collection/collection.dart';
 
 import '../utils/file.dart';
-import '../utils/json.dart';
 import '../utils/uri.dart';
 
 class Dependencies {
@@ -16,12 +15,6 @@ class Dependencies {
 
   const Dependencies(this.dependencies);
 
-  factory Dependencies.fromJson(List<Object?>? jsonList) => Dependencies([
-    if (jsonList != null)
-      for (final dependency in jsonList)
-        fileSystemPathToUri(as<String>(dependency)),
-  ]);
-
   List<String> toJson() => toJsonList(dependencies);
 
   static List<String> toJsonList(List<Uri> dependencies) => [
diff --git a/pkgs/native_assets_cli/lib/src/utils/json.dart b/pkgs/native_assets_cli/lib/src/utils/json.dart
index 9adfbcc975..8f6b0c07e8 100644
--- a/pkgs/native_assets_cli/lib/src/utils/json.dart
+++ b/pkgs/native_assets_cli/lib/src/utils/json.dart
@@ -2,165 +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.
 
-import 'dart:core';
-import 'dart:core' as core;
-import 'dart:io';
-
-T as<T>(Object? object) {
-  if (object is T) {
-    return object;
-  }
-  throw FormatException(
-    "Unexpected value '$object' of type ${object.runtimeType} in JSON. Expected"
-    ' a $T.',
-  );
-}
-
-T get<T>(Map<Object?, Object?> map, String key) {
-  final object = map[key];
-  if (object is T) {
-    return object;
-  }
-  throw FormatException(
-    "Unexpected value '$object' of type ${object.runtimeType} in JSON for key "
-    '$key. Expected a $T.',
-  );
-}
-
-extension MapCast on Map<Object?, Object?> {
-  Map<K, V> formatCast<K, V>() => <K, V>{
-    for (final e in entries) as<K>(e.key): as<V>(e.value),
-  };
-}
-
-extension MapJsonUtils on Map<String, Object?> {
-  String string(String key, {Iterable<String>? validValues}) {
-    final value = get<String>(key);
-    if (validValues != null && !validValues.contains(value)) {
-      throw FormatException(
-        'Json "$key" had value $value but expected one of '
-        '${validValues.join(',')}',
-      );
-    }
-    return value;
-  }
-
-  String? optionalString(String key, {Iterable<String>? validValues}) {
-    final value = getOptional<String>(key);
-    if (value == null) return null;
-    if (validValues != null && !validValues.contains(value)) {
-      throw FormatException(
-        'Json "$key" had value $value but expected one of '
-        '${validValues.join(',')}',
-      );
-    }
-    return value;
-  }
-
-  core.bool bool(String key) => get<core.bool>(key);
-  core.bool? optionalBool(String key) => getOptional<core.bool>(key);
-  core.int int(String key) => get<core.int>(key);
-  core.int? optionalInt(String key) => getOptional<core.int>(key);
-
-  Uri path(String key) => _fileSystemPathToUri(get<String>(key));
-
-  Uri? optionalPath(String key) {
-    final value = getOptional<String>(key);
-    if (value == null) return null;
-    return _fileSystemPathToUri(value);
-  }
-
-  List<String>? optionalStringList(String key) {
-    final value = getOptional<List<Object?>>(key);
-    if (value == null) return null;
-    return value.cast<String>();
-  }
-
-  List<String> stringList(String key) => get<List<Object?>>(key).cast<String>();
-
-  List<Uri>? optionalPathList(String key) {
-    final strings = optionalStringList(key);
-    if (strings == null) {
-      return null;
-    }
-    return [for (final string in strings) _fileSystemPathToUri(string)];
-  }
-
-  List<Object?> list(String key) => get<List<Object?>>(key);
-  List<Object?>? optionalList(String key) => getOptional<List<Object?>>(key);
-  Map<String, Object?> map$(String key) => get<Map<String, Object?>>(key);
-  Map<String, T>? optionalMap<T extends Object?>(String key) {
-    final map_ = getOptional<Map<String, Object?>>(key);
-    if (map_ is Map<String, T>?) return map_;
-    for (final value in map_.values) {
-      if (value is! T) {
-        throw FormatException(
-          'Unexpected value \'$map_\' (${map_.runtimeType}) for key \'.$key\''
-          ' in input file. Expected a ${Map<String, T>}?.',
-        );
-      }
-    }
-    return map_.cast();
-  }
-
-  T get<T extends Object>(String key) {
-    final value = this[key];
-    if (value == null) {
-      throw FormatException('No value was provided for required key: $key');
-    }
-    if (value is T) return value;
-    throw FormatException(
-      'Unexpected value \'$value\' for key \'.$key\' in input file. '
-      'Expected a $T.',
-    );
-  }
-
-  T? getOptional<T extends Object>(String key) {
-    final value = this[key];
-    if (value is T?) return value;
-    throw FormatException(
-      'Unexpected value \'$value\' for key \'.$key\' in input file. '
-      'Expected a $T?.',
-    );
-  }
-
-  void setNested(List<String> nestedMapKeys, Object? value) {
-    var map = this;
-    for (final key in nestedMapKeys.sublist(0, nestedMapKeys.length - 1)) {
-      map = (map[key] ??= <String, Object?>{}) as Map<String, Object?>;
-    }
-    map[nestedMapKeys.last] = value;
-  }
-}
-
-extension ListJsonUtils on List<Object?> {
-  T get<T extends Object>(int index) {
-    final value = this[index];
-    if (value == null) {
-      throw FormatException('No value was provided for index: $index');
-    }
-    if (value is T) return value;
-    throw FormatException(
-      'Unexpected value \'$value\' for index \'.$index\' in input file. '
-      'Expected a $T.',
-    );
-  }
-
-  Map<String, Object?> mapAt(int index) => get<Map<String, Object?>>(index);
-  Uri pathAt(int index) => _fileSystemPathToUri(get<String>(index));
-}
-
-Uri _fileSystemPathToUri(String path) {
-  if (path.endsWith(Platform.pathSeparator)) {
-    return Uri.directory(path);
-  }
-  return Uri.file(path);
-}
-
-extension UriList on List<Uri> {
-  List<String> toJson() => [for (final uri in this) uri.toFilePath()];
-}
-
 extension MapSorting<K extends Comparable<K>, V extends Object?> on Map<K, V> {
   void sortOnKey() {
     final result = <K, V>{};
diff --git a/pkgs/native_assets_cli/test/build_config_test.dart b/pkgs/native_assets_cli/test/build_config_test.dart
index 1e10360da7..47e421f420 100644
--- a/pkgs/native_assets_cli/test/build_config_test.dart
+++ b/pkgs/native_assets_cli/test/build_config_test.dart
@@ -168,7 +168,7 @@ void main() async {
                 e is FormatException &&
                 e.message.contains('Unexpected value') &&
                 e.message.contains(
-                  'Expected a Map<String, Map<String, Object?>>?',
+                  'Expected a Map<String, Map<String, Object?>>',
                 ),
           ),
         ),
diff --git a/pkgs/native_assets_cli/test/link_config_test.dart b/pkgs/native_assets_cli/test/link_config_test.dart
index 4a6d4be499..32785e9a6d 100644
--- a/pkgs/native_assets_cli/test/link_config_test.dart
+++ b/pkgs/native_assets_cli/test/link_config_test.dart
@@ -138,7 +138,7 @@ void main() async {
             (e) =>
                 e is FormatException &&
                 e.message.contains(
-                  "Unexpected value 'astring' for key '.assets' in input file. "
+                  "Unexpected value 'astring' for key '.assets'. "
                   'Expected a List<Object?>?.',
                 ),
           ),