indexing

function add_custom_meta_tags() {

    if (is_single()) {

        global $post;

        echo '<meta name="description" content="' . get_the_excerpt($post) . '">'."\n";

        echo '<meta name="keywords" content="';

        foreach (get_the_tags($post->ID) as $tag) {

            echo $tag->name . ', ';

        }

        echo '">'."\n";

    }

}

add_action('wp_head', 'add_custom_meta_tags');