How to write product requirements engineers actually understand

Engineers do not reject requirements because they are too long or too short. They reject them because the document leaves the hard decisions to be discovered in code review.

A good requirements document is not a description of a feature. It is a record of decisions already made, and an honest list of the ones still open. A description can be vague and still be true. A record of decisions cannot.

Open with the decision that changes

Before anything else, write one sentence: who makes what call today, and what they will do differently once this ships.

If you cannot write that sentence, the document is not ready to be written. That is not a setback — it is the most valuable thing the exercise will tell you all week.

It has a shape: a named role, the decision they make now, and that decision afterward. “A finance clerk checks every supplier invoice against its purchase order by hand; after this ships she sees only the ones the system could not match.”

Two failures show up here. A sentence about the system rather than the person — “the platform will support automated matching” — commits to nothing. And a second half that is the first half in a better mood: if no decision changes, you are building a preference.

Write the non-goals before the goals

This feels backwards and is not. Listing what the feature does not do is easier, it makes the goals honest, and it ends the argument in week three when somebody asks why it does not also handle refunds.

Scope creep is not caused by ambition. It is caused by ambiguity nobody wrote down.

Write non-goals as specific nouns. Not “this release is limited in scope” but “this does not handle credit notes, multi-currency invoices, invoices with no purchase order, or suppliers on payment hold.” Each costs one line now or one argument later.

Write one the moment you catch yourself thinking obviously we are not doing that in version one. If it were obvious, you would not have had the thought.

That is the opening. The rest of the lesson — the remaining sections, the exercise and the check-your-understanding questions — is behind the gate below.