Specification and user journey

This lesson is still being tested: it improves with learners' feedback. If something is unclear, it is the lesson that needs fixing, not you.

By the end of this lesson, you will be able to

turn a need into a one-page specification;
describe the journey of the person who will use the tool;
set a minimum version and checkable criteria;
decide on the tool’s data, and keep only what is needed.

Why it matters to you

An agent can build a tool in a few minutes. But if you don’t know exactly what you want, it will decide for you: the screens, the data, what is sent where. The specification is your order. It fits on one page, it is discussed before building, and you will use it to check the result. It is the same principle as the project sheet in module 6, applied to a tool.

Before you start


You need	Claude Code (app or terminal), in Manual mode, an empty project folder (for example inside `mon-espace-ia/projets`), and the specification template (resource)
Cost	The agent subscription: Claude Pro at minimum, €18 per month excl. VAT billed monthly, or €15 per month excl. VAT with the annual plan of €180 paid up front; prices shown on claude.com/pricing on 24/10/2026
Duration	60 minutes
Reminder	The specification describes the tool’s data: nothing more than what is needed

Understand it in 3 minutes

The parts of a specification (template in the resource):

Part	The question
The problem	What is wrong today?
Who uses it	Who, on which device, at what moment?
The journey	What does the person do, step by step?
The minimum version	What is the smallest tool that already solves the problem?
Out of scope for now	What are we not doing in this version?
It worked if	Which criteria, checkable with a yes or a no?
The data	Which data, where does it stay, what do we not keep?

The journey is told from the person’s point of view: “I open the file, I see the books not yet returned, I type the title and the first name…”. Not “the application displays a table”.

The data. The CNIL (the French data protection authority) advises, before any collection, to think about the types of data that are needed and to limit collection to what is strictly necessary. For a loan logbook, a first name and a title are enough: no address, no phone number.

Simple constraints to start with: a single file, which opens in the browser, with no account, no server, nothing to install, and nothing loaded from the Internet. Everything stays on your computer.

Do it together

1Step 1: The need, in two sentences

The example for this module: the book club wants to know who borrowed which book from its “book box”, and what has not been returned yet. Write your own need in two sentences, or keep this one to practice.

2Step 2: Have the specification proposed

Open Claude Code on your project folder, in Manual mode, and use the request from the resource.

In our test on 24/10/2026, with the club’s need and the seven parts of the table above (the resource template adds two headings, CONSTRAINTS and TO DECIDE), the specification followed those seven parts, with checkable criteria (“I record a loan (title + first name) in under 30 seconds”), marked “[to decide]” what had to be settled (who keeps the logbook, after how many days a book is late), and warned on its own that the data would stay tied to this browser, on this computer, hence a backup to plan. It ended with three questions.

3Step 3: Settle things

Answer the questions, and replace each [to decide] with your decision. Then reread with the checklist from the resource:

can each criterion be checked with a yes or a no?
is the data reduced to what is needed?
does the minimum version fit in one sentence?

4Step 4: Keep the specification

Keep specification.md in the project folder: it is the reference for the next lessons. Write the date at the top.

Your turn

Choose a real small problem: a tracker, a list, a calculation that comes back, an information page.
Have the specification proposed, with your constraints.
Settle each point, and reread with the checklist from the resource.
Keep the specification in the project folder, dated.

Resources to download

Specification template for a small tool: the parts, the request to your agent, and the checklist to reread before building.

Check your work

It worked if:

your specification has its parts, and no [to decide] left;
each criterion can be checked with a yes or a no;
the data is reduced to what is needed, and you know where it stays;
the minimum version fits in one sentence.

Common mistakes:

starting to build “just to see”, before the specification;
a minimum version that already contains everything;
vague criteria (“simple”, “pretty”);
keeping data “just in case”.

Keep it and pick it up later

The specification lives with the project: when you change your mind, change it first, then the tool.
Write your decision and its reason in your journal (module 5, lesson 3).

Going further

optional

The CNIL’s GDPR guide for developers: cnil.fr, “GDPR developer’s guide” (an English version exists).

New words

4 words explained

Word	What it means
Specification	The page that says what the tool must do, and how you will know it worked
User journey	The steps, seen by the person who uses the tool
Minimum version	The smallest tool that already solves the problem
Data minimization	Collecting only the data that is really needed