Custom value in woocommerce webhook payload

Figured out.First add custom field on check out form.

add_action( 'woocommerce_after_order_notes', 'fs_custom_checkout_field' );function fs_custom_checkout_field( $checkout ) {    echo '<div id="my_custom_checkout_field"><h2>' . __('Extra Information') . '</h2>';    woocommerce_form_field( 'fs_psid_field', array(        'type'          => 'text',        'class'         => array('my-field-class form-row-wide'),        'label'         => __('Fill in this field'),        'placeholder'   => __('Enter something'),        ), $checkout->get_value( 'fs_psid_field' ));    echo '</div>';}

Then save custom field's value as meta

add_action( 'woocommerce_checkout_update_order_meta', 'my_custom_checkout_field_update_order_meta' );function my_custom_checkout_field_update_order_meta( $order_id ) {    if ( ! empty( $_POST['fs_psid_field'] ) ) {        update_post_meta( $order_id, 'fs_psid_field', sanitize_text_field( $_POST['fs_psid_field'] ) );    }}

Then add custom field's value in api response

function my_custom_wc_api_order_response( $order_data, $order ) {    $psidMeta      = get_post_meta($order->id , 'fs_psid_field' , true );    $order_data['psid'] = $psidMeta;    return $order_data;}add_filter( 'woocommerce_api_order_response', 'my_custom_wc_api_order_response', 10, 3 );