Wp add description to Featured image box

Wp add description to Featured image box

/**
*  Add description to Featured image box
*/
function admin_post_thumbnail_descr( $content, $post_id, $thumbnail_id ) {
    $caption = '<p style="color: #c04747;">' . esc_html__( 'Minimum image size: ', 'i18n-tag' ) . '</p>';
    $caption2 = '<p style="color: #c04747;">' . esc_html__( 'width:800px; height: 300px;', 'i18n-tag' ) . '</p>';
    return $content . $caption . $caption2;
}
add_filter( 'admin_post_thumbnail_html', 'admin_post_thumbnail_descr', 10, 3 );


Add only selected post type
===========================

function admin_post_thumbnail_descr( $content, $post_id, $thumbnail_id ) {
    if ( 'post' !== get_post_type( $post_id ) ) {
        $caption = '<p>' . esc_html__( 'Recommended image size: 1300px (width) x 340px (height)', 'i18n-tag' ) . '</p>';
        return $content;
    }
}
add_filter( 'admin_post_thumbnail_html', 'admin_post_thumbnail_descr', 10, 3 );