Full guide: What is a System One extraction model? Extraction models explained
Every scalar answer from Clairic carries four fields: value, p_null, confidence and guess. value and guess can be numbers, dates or text. p_null answers one question: is the thing you asked for there at all?
Cloudflare’s support-email example shows why it matters. The email has no tracking number, so the tracking_number field comes back with value null and p_null 1. The guess is “$52.10”, a figure from elsewhere in the email, with a confidence of 0.416. Without p_null your code might take that guess for an answer.
A simple gate reads p_null first. Treat a high value as “not provided” and ask for it. Read confidence only when the value is present.
Cloudflare says calibration “is measured, not guaranteed”, so set thresholds from your own logs. A decision model has no p_null; a Noul question asked about whether a field is present is the nearest equivalent. The extraction model guide covers the full answer shape.