wp_oembed_add_discovery_links

	if ( is_singular() ) {
		$output .= '<link rel="alternate" type="application/json+oembed" href="' . esc_url( get_oembed_endpoint_url( get_permalink() ) ) . '" />' . "\n";

		if ( class_exists( 'SimpleXMLElement' ) ) {
			$output .= '<link rel="alternate" type="text/xml+oembed" href="' . esc_url( get_oembed_endpoint_url( get_permalink(), 'xml' ) ) . '" />' . "\n";
		}
	}

	/**
	 * Filters the oEmbed discovery links HTML.
	 *
	 * @since 4.4.0
	 *
	 * @param string $output HTML of the discovery links.
	 */
	echo apply_filters( 'oembed_discovery_links', $output );
}

/**
 * Adds the necessary JavaScript to communicate with the embedded iframes.