On the preview tab, you can look at the JSON body of the request, with the variables replaced by sample values. Here, you have the ability to copy the JSON to your clipboard in case you want to test the webhook call somewhere else, like Postman. Tonic provides the ability to make a test request, which will include the configured headers and body (variables replaced with sample values), directly from Tonic. Press the "Test Webhook" button in the bottom left at any time to test a webhook configuration.