The seven Day-Zero screens.
Your book, the card, policy, one applicant, the whole book, does it hold, validation.
In the order a lender lives them
The seven screens run top to bottom in the order a lender meets the questions, and each ends with a link to the next. The book picker at the top of every screen switches between the public lending books; the screens keep the choice as you move.
1. Your book
What do you hand over, and what do we never see? A description of the columns: names, types, ranges and a few unlabelled rows. No outcomes, no history. The screen lists every column in the dictionary and whether it is available at decision time.
2. The card
What did it write, and why? The scorecard with its weights, each with the reason it gives for the column's direction of risk, the low, typical and high values it expects, and any derived ratios and scored pairs.
3. Policy
Who sets the grades and the floors? The card proposes; the policy decides. Columns you will not lend on, a floor under the probability of default and the grades in use — every control rescores the book on the spot.
4. One applicant
What does an underwriter see? One application scored and explained in points: the grade, the probability of default and the percentile, and the columns that moved the score. Pick a reference applicant and move any value.
5. The whole book
Where do you put the cut-off? Decline the worst share of applications and see what follows from it: the bad rate of the book you keep, the good business turned away, the defaults still accepted, and the trade-off across every cut-off you could pick.
6. Does it hold
How good is it, measured against outcomes? The card is fixed before the labels are applied. Scoring the sample in the browser reveals how the card ranks against outcomes it never saw, and, where a book carries origination dates, how stable it is over time.
7. Validation
What does your validator get? The card set against the standards a validator works to — what each rule asks, what the card gives, what it does not — with every number traced to a source file and a hash.