Currently the webhook action uses the
remote::request() function from the Kirby Toolkit, which in turn uses the cURL extension to send the request. If a cURL error occurs, the output of
curl_error gets passed through to be available by the
message() function of Uniform.
Unfortunately a response with a HTTP error code (e.g.
4xx) is not an error as far as cURL is concerned so the webhook action definitely can be improved here. But you can easily modify the action to shape it to your needs (you probably have done this already to return the integer response).