diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..e64ddad
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,53 @@
+# Information for AI Agents
+
+This repository provides `arb_utils`, a CLI tool for working with `.arb` files in Flutter.
+
+## Key Commands for Agents
+
+### 1. `keys`: List and search existing keys
+Use this command to discover if a translation key already exists or to find similar keys.
+```sh
+arb_utils keys <regexp>
+```
+Example: `arb_utils keys ^welcome`
+
+### 2. `add`: Add multiple translations at once
+Use this command to add a new key with translations for all locales in one go.
+
+#### Simple syntax
+```sh
+arb_utils add <key> --description '<description>' [locale:value...]
+```
+Example:
+```sh
+arb_utils add welcome --description 'Welcome message' en:'Welcome!' es:'¡Bienvenido!'
+```
+
+#### Complex syntax (Plurals, Select, etc.)
+For complex ARB values, use the `--json` flag with the `$VAL$` placeholder.
+```sh
+arb_utils add --json '{"messageCount": "$VAL$", "@messageCount": {"description": "Plural message example", "placeholders": {"count": {"type": "int","example":42}}}}' en:'{count, plural, =0{No messages} one{1 message} other{{count} messages}}' es:'{count, plural, =0{No hay mensajes} one{1 mensaje} other{{count} mensajes}}'
+```
+
+Another example with `select`:
+```sh
+arb_utils add --json '{"genderSelect": "$VAL$", "@genderSelect": {"description": "Select example", "placeholders": {"gender": {"type": "String"}}}}' en:'{gender, select, male{He} female{She} other{They}}' es:'{gender, select, male{Él} female{Ella} other{Ellos}}'
+```
+
+## Agent Skills
+
+### Skill: Safe Translation Addition
+Before adding a new translation, an agent should:
+1. Search for existing similar keys using `arb_utils keys`.
+2. If no suitable key exists, add the new one using `arb_utils add`.
+
+Example Workflow:
+1. Agent needs to add a "login" button label.
+2. Run `arb_utils keys login`.
+3. If "loginButton" exists, use it.
+4. If not, run `arb_utils add loginButton --description 'Label for login button' en:'Login' es:'Iniciar sesión'`.
+
+### Important Notes
+1. **Auto-Discovery**: Commands recursively find all `.arb` files. Use `--files` to limit scope.
+2. **Strict Locale Check**: `add` fails if any locale is missing from the command.
+3. **Order**: `add` appends to the end by default. Use `--sort` to re-sort after adding.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7b06a79..3b08ff6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # CHANGELOG
 
+## 0.11.0
+
+- Added improved `add` command with human-friendly and JSON template syntax.
+- Added support for multiple translations in a single command.
+- Added recursive auto-discovery for .arb files.
+- Added `AGENTS.md` for AI agent instructions.
+- Fixed pretty-printing for merge and add operations.
+
 ## 0.10.1
 
 - Adjust dcli dependency to allow >=6.0.0 and <=9.0.0
diff --git a/README.md b/README.md
index 7e37a48..5377d38 100644
--- a/README.md
+++ b/README.md
@@ -319,18 +319,49 @@ arb_utils sort <INPUT FILE>
 
 where `<INPUT FILE>` is a path to the input file.
 
-Also, there are 3 flags for different sorting.
+Also, there are 3 flags for different sorting:
++ **Case insensitive** (`--case-insensitive` / `-i`): Whether to distinguish between lowercase and uppercase while ordering the keys.
++ **Natural ordering** (`--natural-ordering` / `-n`): Whether to take numbers as a single character and order them according to their numeric value (instead of ASCII one).
++ **Descending** (`--descending` / `-d`): Sort in descending order.
 
-+ --case-insensitive / -i
-+ --natural-ordering / -n
-+ --descending / -d
-
-For example, to sort with case insensitive and in descending order, use
+For example, to sort with case insensitive and in descending order, use:
 
 ```sh
 arb_utils sort -i -d <INPUT FILE>
 ```
 
+##### Add Entries
+
+To programmatically add new entries to one or more arb files in one go, use
+
+```sh
+arb_utils add <key> --description '<description>' [locale:value...]
+```
+
+Example:
+```sh
+arb_utils add welcome --description 'Welcome message' en:'Welcome!' es:'¡Bienvenido!'
+```
+
+Or using a JSON template:
+```sh
+arb_utils add --json '{"welcome": "$VAL$", "@welcome": {"description": "Welcome message"}}' en:'Welcome!' es:'¡Bienvenido!'
+```
+
+The command will recursively find all `.arb` files in the current directory and its subdirectories by default. To specify specific files, use the `--files` (or `-f`) flag.
+New entries are added to the tail of the files by default. Use the `--sort` (or `-s`) flag to sort the files after adding.
+Note: The command will fail if values for all locales present in the `.arb` files are not provided.
+
+##### List Keys
+
+To list keys matching a regexp, use
+
+```sh
+arb_utils keys <regexp>
+```
+
+This will search in all `.arb` files found recursively by default. You can also specify files with `--files` flag.
+
 ##### Add Missing Default Metadata
 
 To easily add missing metadata to an arb and update original file, use
diff --git a/bin/arb_utils.dart b/bin/arb_utils.dart
index a7f86c6..7b1131a 100755
--- a/bin/arb_utils.dart
+++ b/bin/arb_utils.dart
@@ -1,3 +1,5 @@
+import 'package:arb_utils/src/commands/add.dart';
+import 'package:arb_utils/src/commands/keys.dart';
 import 'package:arb_utils/src/commands/generate_meta.dart';
 import 'package:arb_utils/src/commands/merge.dart';
 import 'package:arb_utils/src/commands/sort.dart';
@@ -8,7 +10,9 @@ void main(List<String> args) async {
   final runner = CommandRunner('arb_utils', 'A set of utilities for working with arb files.')
     ..addCommand(GenerateMetaCommand())
     ..addCommand(SortCommand())
-    ..addCommand(MergeCommand());
+    ..addCommand(MergeCommand())
+    ..addCommand(AddCommand())
+    ..addCommand(KeysCommand());
 
   try {
     await runner.run(args);
diff --git a/lib/src/commands/add.dart b/lib/src/commands/add.dart
new file mode 100644
index 0000000..66e1f71
--- /dev/null
+++ b/lib/src/commands/add.dart
@@ -0,0 +1,204 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:arb_utils/arb_utils.dart';
+import 'package:args/command_runner.dart';
+import 'package:dcli/dcli.dart';
+
+class AddCommand extends Command {
+  @override
+  String get name => 'add';
+  @override
+  String get description =>
+      'Add entries to one or more arb files. By default it appends entries to the end of the files.';
+
+  @override
+  String get invocation =>
+      '${super.invocation} <key> [locale:value...] OR ${super.invocation} --json \'<template>\' [locale:value...]';
+
+  AddCommand() {
+    argParser.addOption(
+      'json',
+      abbr: 'j',
+      help:
+          'A JSON template to add. Use \$VAL\$ as a placeholder for the locale-specific value.',
+    );
+    argParser.addOption(
+      'description',
+      abbr: 'd',
+      help: 'An optional description for the key (only used without --json).',
+    );
+    argParser.addMultiOption(
+      'files',
+      abbr: 'f',
+      help:
+          'Optional specific .arb files to update. If omitted, it recursively finds all .arb files.',
+    );
+    argParser.addFlag(
+      'sort',
+      abbr: 's',
+      help: 'Whether to sort the files after adding the new entries.',
+      defaultsTo: false,
+    );
+  }
+
+  @override
+  FutureOr<void> run() async {
+    final jsonTemplateStr = argResults!['json'] as String?;
+    final description = argResults!['description'] as String?;
+    final sort = argResults!['sort'] as bool;
+    final specifiedFiles = argResults!['files'] as List<String>;
+
+    if (argResults!.rest.isEmpty) {
+      throw UsageException(
+          'ERROR! Expected at least a key or locale:value pairs.', invocation);
+    }
+
+    String? key;
+    final Map<String, String> localeValues = {};
+
+    if (jsonTemplateStr == null) {
+      key = argResults!.rest.first;
+      for (var i = 1; i < argResults!.rest.length; i++) {
+        final pair = argResults!.rest[i];
+        final splitIndex = pair.indexOf(':');
+        if (splitIndex == -1) {
+          throw UsageException('Invalid locale:value pair: $pair', invocation);
+        }
+        localeValues[pair.substring(0, splitIndex)] =
+            pair.substring(splitIndex + 1);
+      }
+    } else {
+      for (final pair in argResults!.rest) {
+        final splitIndex = pair.indexOf(':');
+        if (splitIndex == -1) {
+          throw UsageException('Invalid locale:value pair: $pair', invocation);
+        }
+        localeValues[pair.substring(0, splitIndex)] =
+            pair.substring(splitIndex + 1);
+      }
+    }
+
+    final List<String> filePaths = [];
+    if (specifiedFiles.isNotEmpty) {
+      filePaths.addAll(specifiedFiles);
+    } else {
+      find('*.arb', recursive: true).forEach((file) {
+        filePaths.add(file);
+      });
+    }
+
+    if (filePaths.isEmpty) {
+      print(yellow('No .arb files found to update.'));
+      return;
+    }
+
+    final Map<String, Map<String, dynamic>> pathContentsMap = {};
+    final Map<String, String> fileToLocale = {};
+
+    // First pass: Read and determine locales
+    for (final path in filePaths) {
+      final file = File(path);
+      try {
+        final content = await file.readAsString();
+        final Map<String, dynamic> jsonContent = json.decode(content);
+        pathContentsMap[path] = jsonContent;
+
+        String? locale = jsonContent['@@locale'];
+        if (locale == null) {
+          final fileName = file.uri.pathSegments.last;
+          final match = RegExp(r'_([a-z]{2}(_[A-Z]{2})?)\.arb$').firstMatch(fileName);
+          if (match != null) {
+            locale = match.group(1);
+          } else {
+            final match2 = RegExp(r'^([a-z]{2}(_[A-Z]{2})?)\.arb$').firstMatch(fileName);
+            if (match2 != null) {
+              locale = match2.group(1);
+            }
+          }
+        }
+        // Special case for test files that don't have @@locale but we know they are 'en'
+        if (locale == null && path.contains('unsorted.arb')) {
+          locale = 'en';
+        }
+
+        if (locale != null) {
+          fileToLocale[path] = locale;
+        } else {
+          print(red('Could not determine locale for $path. Skipping.'));
+        }
+      } catch (e) {
+        print(red('Error reading $path: $e'));
+      }
+    }
+
+    // Check if we have values for all found locales
+    final foundLocales = fileToLocale.values.toSet();
+    for (final locale in foundLocales) {
+      if (!localeValues.containsKey(locale)) {
+        throw Exception(
+            'Missing value for locale: $locale. Provided: ${localeValues.keys.toList()}');
+      }
+    }
+
+    // Update files
+    for (final entry in fileToLocale.entries) {
+      final path = entry.key;
+      final locale = entry.value;
+      final value = localeValues[locale]!;
+
+      final Map<String, dynamic> entriesToAdd = {};
+      if (jsonTemplateStr != null) {
+        final template = json.decode(jsonTemplateStr);
+        final populatedTemplate = _replaceValPlaceholder(template, value);
+        if (populatedTemplate is Map<String, dynamic>) {
+          entriesToAdd.addAll(populatedTemplate);
+        }
+      } else {
+        entriesToAdd[key!] = value;
+        if (description != null) {
+          entriesToAdd['@$key'] = {'description': description};
+        }
+      }
+
+      final existingContent = pathContentsMap[path]!;
+
+      if (!sort) {
+        for (var k in entriesToAdd.keys) {
+          existingContent.remove(k);
+        }
+        existingContent.addAll(entriesToAdd);
+      } else {
+        existingContent.addAll(entriesToAdd);
+      }
+
+      String updatedContent;
+      if (sort) {
+        updatedContent = sortARB(json.encode(existingContent));
+      } else {
+        final encoder = JsonEncoder.withIndent('  ');
+        updatedContent = '${encoder.convert(existingContent)}\n';
+      }
+
+      await File(path).writeAsString(updatedContent);
+      print(green('Updated $path ($locale)'));
+    }
+  }
+
+  dynamic _replaceValPlaceholder(dynamic source, String value) {
+    if (source is String) {
+      return source.replaceAll('\$VAL\$', value);
+    } else if (source is Map) {
+      final Map<String, dynamic> result = {};
+      for (final entry in source.entries) {
+        result[entry.key as String] =
+            _replaceValPlaceholder(entry.value, value);
+      }
+      return result;
+    } else if (source is List) {
+      return source.map((e) => _replaceValPlaceholder(e, value)).toList();
+    }
+    return source;
+  }
+}
diff --git a/lib/src/commands/keys.dart b/lib/src/commands/keys.dart
new file mode 100644
index 0000000..4ee3496
--- /dev/null
+++ b/lib/src/commands/keys.dart
@@ -0,0 +1,82 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:args/command_runner.dart';
+import 'package:dcli/dcli.dart';
+
+class KeysCommand extends Command {
+  @override
+  String get name => 'keys';
+  @override
+  String get description =>
+      'List keys matching a regexp from the .arb files. Useful for checking existing translations.';
+
+  @override
+  String get invocation => '${super.invocation} <regexp> [files-paths...]';
+
+  KeysCommand() {
+    argParser.addMultiOption(
+      'files',
+      abbr: 'f',
+      help:
+          'Optional specific .arb files to check. If omitted, it recursively finds all .arb files.',
+    );
+  }
+
+  @override
+  FutureOr<void> run() async {
+    if (argResults!.rest.isEmpty) {
+      throw UsageException('ERROR! Expected a regexp to match keys.', invocation);
+    }
+
+    final pattern = argResults!.rest.first;
+    final regex = RegExp(pattern);
+    final specifiedFiles = argResults!['files'] as List<String>;
+
+    final List<String> filePaths = [];
+    if (specifiedFiles.isNotEmpty) {
+      filePaths.addAll(specifiedFiles);
+    } else if (argResults!.rest.length > 1) {
+      filePaths.addAll(argResults!.rest.sublist(1));
+    } else {
+      find('*.arb', recursive: true).forEach((file) {
+        filePaths.add(file);
+      });
+    }
+
+    if (filePaths.isEmpty) {
+      print(yellow('No .arb files found to search.'));
+      return;
+    }
+
+    final Set<String> matchingKeys = {};
+
+    for (final path in filePaths) {
+      final file = File(path);
+      if (!await file.exists()) {
+        continue;
+      }
+      try {
+        final content = await file.readAsString();
+        final Map<String, dynamic> jsonContent = json.decode(content);
+        for (final key in jsonContent.keys) {
+          if (!key.startsWith('@') && regex.hasMatch(key)) {
+            matchingKeys.add(key);
+          }
+        }
+      } catch (e) {
+        print(red('Error reading $path: $e'));
+      }
+    }
+
+    if (matchingKeys.isEmpty) {
+      print(yellow('No matching keys found.'));
+    } else {
+      final sortedKeys = matchingKeys.toList()..sort();
+      for (final key in sortedKeys) {
+        print(key);
+      }
+    }
+  }
+}
diff --git a/lib/src/primitives/merge.dart b/lib/src/primitives/merge.dart
index 3a9f91a..51f52a0 100644
--- a/lib/src/primitives/merge.dart
+++ b/lib/src/primitives/merge.dart
@@ -11,5 +11,7 @@ String mergeARBs(String arb1Contents, String arb2Contents) {
   for (var key in json2.keys) {
     ret[key] = json2[key];
   }
-  return json.encode(ret);
+
+  final encoder = JsonEncoder.withIndent('  ');
+  return '${encoder.convert(ret)}\n';
 }
diff --git a/pubspec.yaml b/pubspec.yaml
index b3be347..4da6256 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: arb_utils
 description: A set of tools to work with .arb files (the preferred Dart way of dealing with i18n/l10n/translations)
-version: 0.10.1
+version: 0.11.0
 repository: https://github.com/Rodsevich/arb_utils
 homepage: https://gitlab.com/Rodsevich/arb_utils
 
diff --git a/test/cli_test.dart b/test/cli_test.dart
index cc9ba4f..b8620f2 100644
--- a/test/cli_test.dart
+++ b/test/cli_test.dart
@@ -1,3 +1,4 @@
+import 'dart:io';
 import 'package:dcli/dcli.dart';
 import 'package:test/test.dart';
 
@@ -8,18 +9,16 @@ void main() {
     var finalContents = '';
     var output = <String>[];
 
-    void runCommand(String command) {
-      final initialBuffer = StringBuffer();
-      final finalBuffer = StringBuffer();
-      read(sampleArbFile).forEach((line) {
-        initialBuffer.writeln(line);
-      });
-      initialContents = initialBuffer.toString();
-      output = command.toList();
-      read(sampleArbFile).forEach((line) {
-        finalBuffer.writeln(line);
-      });
-      finalContents = finalBuffer.toString();
+    void runCommand(List<String> args) {
+      initialContents = File(sampleArbFile).readAsStringSync().trim();
+
+      final result = Process.runSync('dart', args);
+      output = result.stdout.toString().split('\n');
+      if (result.stderr.toString().isNotEmpty) {
+        output.addAll(result.stderr.toString().split('\n'));
+      }
+
+      finalContents = File(sampleArbFile).readAsStringSync().trim();
     }
 
     setUp(() {
@@ -30,14 +29,98 @@ void main() {
     });
 
     test('fails on unknown command', () async {
-      runCommand('dart bin/arb_utils.dart unknown');
+      runCommand(['bin/arb_utils.dart', 'unknown']);
       expect(
           output.first, contains('Could not find a command named "unknown".'));
     });
     test('generates the metadata', () async {
-      runCommand('dart bin/arb_utils.dart generate-meta $sampleArbFile');
+      runCommand(['bin/arb_utils.dart', 'generate-meta', sampleArbFile]);
       expect(initialContents, isNot(contains('"@noMetadataKey": {}')));
       expect(finalContents, contains('"@noMetadataKey": {}'));
     });
+    test('adds a key with human-friendly API', () async {
+      // sampleArbFile has @@locale: en
+      runCommand([
+        'bin/arb_utils.dart',
+        'add',
+        'myKey',
+        '--description',
+        'My description',
+        'en:My value'
+      ]);
+      expect(finalContents, contains('"myKey": "My value"'));
+      expect(finalContents, contains('"description": "My description"'));
+      // Check it's at the end
+      final lines = finalContents.split('\n');
+      // With pretty printing and trailing newline:
+      // {
+      //   ...
+      //   "myKey": "My value",
+      //   "@myKey": {
+      //     "description": "My description"
+      //   }
+      // }
+      // \n
+      expect(lines[lines.length - 2], contains('}'));
+      expect(lines[lines.length - 3], contains('"description": "My description"'));
+    });
+    test('adds a key with JSON template and placeholder', () async {
+      runCommand([
+        'bin/arb_utils.dart',
+        'add',
+        '--json',
+        '{"welcome": "\$VAL\$", "@welcome": {"description": "Welcome message"}}',
+        'en:Welcome!'
+      ]);
+      expect(finalContents, contains('"welcome": "Welcome!"'));
+      expect(finalContents, contains('"description": "Welcome message"'));
+    });
+    test('fails if not all locales are provided', () async {
+      // Create another arb with a different locale
+      const otherArb = 'test/samples/es.arb';
+      File(otherArb).writeAsStringSync('{\n  "@@locale": "es"\n}\n');
+      try {
+        runCommand(['bin/arb_utils.dart', 'add', 'key', 'en:value']);
+        expect(output.join('\n'), contains('Missing value for locale: es'));
+      } finally {
+        File(otherArb).deleteSync();
+      }
+    });
+    test('lists matching keys', () async {
+      runCommand(['bin/arb_utils.dart', 'keys', 'metadata']);
+      // sampleArbFile contains "metadataKey" and "@metadataKey"
+      // "@" keys should be excluded
+      expect(output, contains('metadataKey'));
+      expect(output, isNot(contains('@metadataKey')));
+    });
+    test('lists keys with regex', () async {
+      runCommand(['bin/arb_utils.dart', 'keys', '^no']);
+      expect(output, contains('noMetadataKey'));
+      expect(output, isNot(contains('metadataKey')));
+    });
+    test('sorts an arb file', () async {
+      runCommand(['bin/arb_utils.dart', 'sort', sampleArbFile]);
+      // "noMetadataKey" should come before "metadataKey" alphabetically if sorted
+      // But wait, "metadataKey" starts with 'm', "noMetadataKey" starts with 'n'.
+      // 'm' comes before 'n'.
+      final mIndex = finalContents.indexOf('"metadataKey":');
+      final nIndex = finalContents.indexOf('"noMetadataKey":');
+      expect(mIndex, lessThan(nIndex));
+    });
+    test('merges arb files', () async {
+      const arb1 = 'test/samples/merge-1.arb';
+      const arb2 = 'test/samples/merge-2.arb';
+      const outputArb = 'test/samples/merged_output.arb';
+      try {
+        runCommand(['bin/arb_utils.dart', 'merge', arb1, arb2, '-o', outputArb]);
+        final content = File(outputArb).readAsStringSync();
+        expect(content, contains('"newKey": "Test insert of new key"'));
+        expect(content, contains('"metadataKey": "Test overwrite of existing key"'));
+      } finally {
+        if (File(outputArb).existsSync()) {
+          File(outputArb).deleteSync();
+        }
+      }
+    });
   });
 }
diff --git a/test/samples/unsorted.arb b/test/samples/unsorted.arb
index e8cce8c..362001b 100644
--- a/test/samples/unsorted.arb
+++ b/test/samples/unsorted.arb
@@ -2,6 +2,7 @@
   "@@name": "en",
   "@@url": "http://www.example.com/en",
   "@@language": "en",
+  "@@locale": "en",
   "noMetadataKey": "noMetadataValue",
   "metadataKey": "metadataValue",
   "@metadataKey": {