Write the model documentation before you need it

There is a predictable moment in the life of a deployed model when someone senior asks how a decision was reached, and the honest answer is that nobody wrote it down. The work of reconstructing it is the same work that would have taken an afternoon before launch. It simply now happens under scrutiny, on a deadline, with a legal team reading over a shoulder.

The minimum that survives an audit

• What the system is for, in one paragraph, including what it is explicitly not for.
• The data it was trained or grounded on, with provenance and the date of the last refresh.
• The evaluation results, with the model version they refer to.
• The human in the loop, if any: who reviews what, and what authority they have to override.
• The incident path: who is called, and what they are empowered to switch off.

None of this requires a regulatory framework to justify. It is the record any engineer would want if they inherited the system on a Monday morning.

Why teams skip it

Because documentation is treated as a deliverable rather than a design tool. Written early, the list above surfaces disagreements while they are still cheap: two people on the same team frequently discover they had different answers to “what is this for”.

Written late, it is an archaeology exercise, and it produces a document nobody trusts.

We put this in the first week of the governance track for the same reason the evaluation track starts with the harness. The order in which you do the work changes what the work is.