// サムネにアイキャッチを使用
add_action( 'wp_head', 'add_meta_to_head' );
function add_meta_to_head() {
	echo '<meta name="thumbnail" content="' .wp_get_attachment_url( get_post_thumbnail_id() ). '" />';
}{"id":89,"count":3,"description":"","link":"https:\/\/riekoshimizu.com\/tag\/%e5%a6%8a%e5%a9%a6\/","name":"\u598a\u5a66","slug":"%e5%a6%8a%e5%a9%a6","taxonomy":"post_tag","meta":[],"_links":{"self":[{"href":"https:\/\/riekoshimizu.com\/wp-json\/wp\/v2\/tags\/89"}],"collection":[{"href":"https:\/\/riekoshimizu.com\/wp-json\/wp\/v2\/tags"}],"about":[{"href":"https:\/\/riekoshimizu.com\/wp-json\/wp\/v2\/taxonomies\/post_tag"}],"wp:post_type":[{"href":"https:\/\/riekoshimizu.com\/wp-json\/wp\/v2\/posts?tags=89"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}