Why is the body of my HTTP request null even though the ServiceNow Outbound REST API is triggering correctly?

Question

Getting the body of an HTTP request from a ServiceNow Outbound REST API.

I cannot seem to get the body of the request correct. The API triggers correctly, but the parameters I am expecting to see (number, short description and state) are coming through as null?

This is my current Business Rule code. - I am using this to trigger a Power Automate flow using the "When an HTTP request is received". The flow triggers, but the body of the request is null when it should contain the number, short description and state values.

(function executeRule(current, previous /*null when async*/) {

    // Define HTTP request settings
    var request = new sn_ws.RESTMessageV2();
    request.setHttpMethod('post');

    // Define the endpoint URL
    request.setEndpoint('my redacted endpoint');

    // Set the request body
    request.setRequestBody(JSON.stringify({
        'number': current.number.toString(),
        'short_description': current.short_description.toString(),
        'state': current.state.toString()
    }));

    // Send the HTTP request and get the response
    var response = request.execute();
    var httpResponseStatus = response.getStatusCode();
    var httpResponseContentType = response.getHeader('Content-Type');
    var parser;
    var obj;

    if (httpResponseStatus === 200) {
        var responseBody = response.getBody();
        parser = new global.JSONParser();
        obj = parser.parse(responseBody);

        // Log success message
        gs.info('HTTP request sent successfully: ' + JSON.stringify(obj));
    } else {
        // Log error message
        gs.error('HTTP request failed with status: ' + httpResponseStatus);
    }

})(current, previous);