diff --git a/src/ASMP.php b/src/ASMP.php
index 93375ca..3380f5b 100644
--- a/src/ASMP.php
+++ b/src/ASMP.php
@@ -11,6 +11,7 @@
 namespace ASMP\WordPressIntegration;
 
 interface ASMP {
-	public const VERSION = 'ASMP_DISCOVERY_VERSION';
+
+	public const VERSION  = 'ASMP_DISCOVERY_VERSION';
 	public const ENDPOINT = 'ASMP_DISCOVERY_ENDPOINT';
 }
diff --git a/src/Console/AsmpCommand.php b/src/Console/AsmpCommand.php
index 8a1f298..121a74d 100644
--- a/src/Console/AsmpCommand.php
+++ b/src/Console/AsmpCommand.php
@@ -9,6 +9,7 @@
 
 namespace ASMP\WordPressIntegration\Console;
 
+use ASMP\WordPressIntegration\ASMP;
 use WP_CLI;
 
 final class AsmpCommand {
@@ -16,30 +17,30 @@ final class AsmpCommand {
 	/**
 	 * Run a check against ASMP.
 	 *
-	 * @param array $args Positional arguments.
-	 * @param array $assoc_args Associative arguments.
+	 * @param array $args       Optional. Array of positional arguments.
+	 * @param array $assoc_args Optional. Array of associative arguments.
 	 */
-	public function check( array $args, array $assoc_args ) {
+	public function check( array $args, array $assoc_args ): void {
 		WP_CLI::error( 'Not implemented yet' );
 	}
 
 	/**
 	 * Request a change through ASMP.
 	 *
-	 * @param array $args Positional arguments.
-	 * @param array $assoc_args Associative arguments.
+	 * @param array $args       Optional. Array of positional arguments.
+	 * @param array $assoc_args Optional. Array of associative arguments.
 	 */
-	public function change( array $args, array $assoc_args ) {
+	public function change( array $args = [], array $assoc_args = [] ): void {
 		WP_CLI::error( 'Not implemented yet' );
 	}
 
 	/**
 	 * Roll back a change through ASMP.
 	 *
-	 * @param array $args Positional arguments.
-	 * @param array $assoc_args Associative arguments.
+	 * @param array $args       Optional. Array of positional arguments.
+	 * @param array $assoc_args Optional. Array of associative arguments.
 	 */
-	public function rollback( array $args, array $assoc_args ) {
+	public function rollback( array $args = [], array $assoc_args = [] ): void {
 		WP_CLI::error( 'Not implemented yet' );
 	}
 
@@ -51,10 +52,39 @@ public function rollback( array $args, array $assoc_args ) {
 	 * <id>
 	 * : ID of the change to roll back.
 	 *
-	 * @param array $args Positional arguments.
-	 * @param array $assoc_args Associative arguments.
+	 * @param array $args       Optional. Array of positional arguments.
+	 * @param array $assoc_args Optional. Array of associative arguments.
 	 */
-	public function status( array $args, array $assoc_args ) {
+	public function status( array $args = [], array $assoc_args = [] ): void {
 		WP_CLI::error( 'Not implemented yet' );
 	}
+
+	/**
+	 * Check whether ASMP is available.
+	 *
+	 * @subcommand is-available
+	 * @param array $args       Optional. Array of positional arguments.
+	 * @param array $assoc_args Optional. Array of associative arguments.
+	 */
+	public function is_available( array $args = [], array $assoc_args = [] ): void {
+		if ( false === \getenv( ASMP::VERSION ) ) {
+			exit( 1 );
+		}
+
+		exit( 0 );
+	}
+
+	/**
+	 * Get the supported version of ASMP.
+	 *
+	 * @param array $args       Optional. Array of positional arguments.
+	 * @param array $assoc_args Optional. Array of associative arguments.
+	 */
+	public function version( array $args = [], array $assoc_args = [] ): void {
+		if ( ! $this->is_available() ) {
+			WP_CLI::error( 'ASMP is not available.' );
+		}
+
+		WP_CLI::log( \getenv( ASMP::VERSION ) );
+	}
 }