Add Meta Header in Head Tag for Single Post

/* Add Meta Header in Head Tag for Single Post */
function add_meta_header() {
    if ( is_single() ) {
        ?>
        <meta content='Germany' property='og:tag' />
        <meta content='Munich' property='og:tag' />
        <?php
    }
}

add_action( 'wp_head', 'add_meta_header' );