Optional. Receives the same digest as JSON (POST, https only, public addresses only, redirects are not followed) - for n8n, Make, Zapier or your own endpoint. Other URLs are refused before anything is read or charged (the run ends as aborted, Invalid input). Each delivery carries an idempotencyKey (also as the Idempotency-Key header). The body is kept under 1 MB: above that each competitor lists its top 5 new ads (with the full count) and what still does not fit is counted in truncated (every row is in the dataset). Stored as a secret. If a delivery fails, the run still ends as succeeded after the checks and charges (the new ads are in the dataset; the status message starts with the failed notification), and a summary of it is sent to this same URL with the next run (a digest with no new ads or signals has nothing to send again). If you change this URL, what was still undelivered for the old one goes to the new one for the competitors still watched under the same label and client (the rest is said in the status message). Temporary failures (timeouts, HTTP 408, 429, 5xx) do not stop the run; if the URL refuses the digest 3 runs in a row with a permanent answer (HTTP 3xx/4xx other than 408/429, or an internal address at connect time), that run ends as aborted and the status message asks to check this URL (one successful delivery resets the count).