diff --git a/lib/WCTokyo/WpCheckin/Command.php b/lib/WCTokyo/WpCheckin/Command.php
index 6fdaef5..531d6f5 100644
--- a/lib/WCTokyo/WpCheckin/Command.php
+++ b/lib/WCTokyo/WpCheckin/Command.php
@@ -20,12 +20,9 @@ class Command extends \WP_CLI_Command {
 	 * @return void
 	 */
 	public function is_valid() {
-		$me = $this->rest_request( '/wp/v2/users/me', 'GET', [
+		$me    = $this->rest_request( '/wp/v2/users/me', 'GET', [
 			'context' => 'edit',
 		] );
-		if ( is_wp_error( $me ) ) {
-			\WP_CLI::error( $me->get_error_message() );
-		}
 		$table = new Table();
 		$table->setHeaders( [ 'Property', 'Value' ] );
 		foreach ( $me as $key => $value ) {
@@ -42,4 +39,30 @@ public function is_valid() {
 		$table->display();
 		\WP_CLI::success( __( 'ユーザー情報を取得しました。', 'wp-checkin' ) );
 	}
+
+	/**
+	 * Display API.
+	 *
+	 * @return void
+	 */
+	public function namespaces() {
+		$response = $this->rest_request( '/' );
+		foreach ( $response['namespaces'] as $namespace ) {
+			\WP_CLI::line( sprintf( '%s/wp-json/%s', trailingslashit( get_option( 'wordcamp_site_url' ) ), $namespace ) );
+		}
+		\WP_CLI::line( '' );
+		// translators: %d is number of namespaces.
+		\WP_CLI::success( sprintf( __( '%dの名前空間があります。', 'wp-checkin' ), count( $response['namespaces'] ) ) );
+	}
+
+	/**
+	 * {@see Request::rest_request()}
+	 */
+	private function request( $path, $method = 'GET', $data = [] ) {
+		$response = $this->rest_request( $path, $method, $data );
+		if ( is_wp_error( $response ) ) {
+			\WP_CLI::error( $response->get_error_message() );
+		}
+		return $response;
+	}
 }
diff --git a/lib/WCTokyo/WpCheckin/Screen/Setting.php b/lib/WCTokyo/WpCheckin/Screen/Setting.php
index 5e470e3..bc2d65f 100644
--- a/lib/WCTokyo/WpCheckin/Screen/Setting.php
+++ b/lib/WCTokyo/WpCheckin/Screen/Setting.php
@@ -30,7 +30,7 @@ public function register_option() {
 			'wp_checkin_settings',
 			__( 'WordCamp チェックイン設定', 'wp-checkin' ),
 			function() {
-				printf( '<p>%s</p>',  esc_html__( 'WordCampのチェックインシステムに必要な設定を行います。', 'wp-checkin' ) );
+				printf( '<p>%s</p>', esc_html__( 'WordCampのチェックインシステムに必要な設定を行います。', 'wp-checkin' ) );
 			},
 			'general'
 		);
diff --git a/lib/WCTokyo/WpCheckin/Utilities/Request.php b/lib/WCTokyo/WpCheckin/Utilities/Request.php
index f32bbe9..449021a 100644
--- a/lib/WCTokyo/WpCheckin/Utilities/Request.php
+++ b/lib/WCTokyo/WpCheckin/Utilities/Request.php
@@ -24,7 +24,7 @@ protected function rest_request( $path, $method = 'GET', $data = [] ) {
 				'status' => 400,
 			] );
 		}
-		$url = get_option( 'wordcamp_site_url' );
+		$url  = get_option( 'wordcamp_site_url' );
 		$user = get_option( 'wordcamp_user_login' );
 		$pass = get_option( 'application_password' );
 		if ( ! $url || ! $user || ! $pass ) {
@@ -33,7 +33,7 @@ protected function rest_request( $path, $method = 'GET', $data = [] ) {
 			] );
 		}
 		$endpoint = trailingslashit( $url ) . 'wp-json/' . ltrim( $path, '/' );
-		$args = [
+		$args     = [
 			'method'  => $method,
 			'timeout' => (int) apply_filters( 'wp_checkin_timeout', 30, $path, $method, $data ),
 			'headers' => [