Where a quick draft falls apart
A rushed use case skips the exception flows, forgets which step an alternate branches from, and quietly invents a business rule to fill a gap. None of that shows up until a developer or tester hits the case it doesn't cover. Numbering the steps properly, and flagging what wasn't actually stated, is most of the value here.
What it does
- Full structure per use case. Primary and supporting actors, stakeholders and interests, preconditions, trigger, numbered main scenario, alternate and exception flows, postconditions.
- Alternates branch correctly. Every alternate or exception flow references the specific numbered step it branches from, using that step's number.
- Plain-tense, no UI clutter. Steps read as "<Actor> …" / "<System> …" in present tense, without naming specific buttons or widgets that will change.
- One goal per use case. A description covering two goals gets split into two use cases, explicitly.
- Never invents a rule. Business rules implied but not stated are flagged
[BR-?? TO CONFIRM]rather than guessed at.
Example
Made up for illustration, not a real client system.
A returning customer logs in and reorders a previous order. If a line item is now out of stock, they need to be able to swap it or drop it before checkout.
UC-01 — Reorder a previous order
Primary actor: Returning Customer
Trigger: customer selects "Reorder"
Main success scenario:
1. Customer selects a past order
2. System loads line items and
current prices
3. System checks stock for each item
4. Customer confirms and checks out
Alternate flows:
3a. Item out of stock → offer swap
or removal, return to step 4
Postconditions: new order created
with confirmed, in-stock items
How it works with Claude
One-time install into Claude, about 10 minutes.
Describe the workflow or interaction you need documented.
Get the numbered use case, plus a use case index table, back.
FAQs
What should a good use case document include?
A primary actor, preconditions, a numbered main success scenario, alternate and exception flows branching from specific step numbers, postconditions, and any business rules the flow depends on.
Can AI write use cases without inventing business rules?
A well-built skill will flag implied-but-unstated rules as open questions rather than guessing at them, and will split a description that actually contains two goals into two separate use cases.