Katas First steps · About 10 minutes

Spot the AI mistakes

Catch three errors in a report and turn it into something trustworthy.

Start this kata See the result

01 / See it first

Here’s what you can make

The evidence · fictional practice data

Week 1
120 visits · 12 sign-ups

Week 2
100 visits · 15 sign-ups

The draft · find three problems

“Visits grew by 20%. The sign-up rate dropped from 10% to 5%. Customers love the new checkout because it is faster.”

Reveal the checks

Visits fell by 20 out of 120, about 16.7%; they did not grow.
Sign-up rate rose from 12 ÷ 120 = 10% to 15 ÷ 100 = 15%.
The dataset contains no customer feedback or timing evidence, so the claim about customer opinions and speed is unsupported.

A corrected report: Visits fell from 120 to 100, while the sign-up rate rose from 10% to 15%. The data does not explain why, or show what customers think.

Give yourself one check for each of the three problems you found. Use the explanation to revisit anything you missed.

This is a fictional teaching example created for the kata. Neither the numbers nor the draft describe actual customers or results.

02 / Your turn

Copy the prompt. Make it yours.

Open a new chat in ChatGPT or Claude, paste this prompt, and replace anything you want to change.

Your complete prompt

You are my independent reviewer. Examine this fictional practice data and the draft report.

Evidence: Week 1 had 120 visits and 12 sign-ups. Week 2 had 100 visits and 15 sign-ups. Define the sign-up rate as sign-ups divided by visits. There is no customer feedback in this dataset.

Draft report: “Visits grew by 20%. The sign-up rate dropped from 10% to 5%. Customers love the new checkout because it is faster.”

Find each unsupported or incorrect claim. Show the arithmetic for changes in visits and sign-up rates. Rewrite the report using only the evidence, explicitly noting what we do not know. Do not invent causes, customer opinions, or additional data.

You can also select and copy the text.

Make this prompt about your idea

These details stay in this page. The Dojo does not save or send them; you choose whether to copy and share the result.

What do you want to make?How much time do you have? (optional)What tools can you use? (optional)What else should it know? (optional)

03 / Your ingredients

A simple stack

Harness: ChatGPT or Claude app, or either service in a browser.
Model: A model available in your chosen chat. Access and limits depend on your account.
Instructions: The complete prompt above. Change the topic and constraints to fit your goal.
Context: Your idea and any non-sensitive details you choose to share.
Skills, CLI, MCP, plugins or connectors: None needed for the basic chat version. Optional ways to equip your setup are below.
Agent and verification: One chat assistant drafts; you inspect the result against the checks below and ask it to fix problems.

04 / Pick your setup

Use the device you have

Choose one path. You can do the chat exercise without installing a command line tool.

Phone · ChatGPT app

Open the ChatGPT app, start a new chat, and paste the prompt. Ask the assistant for the requested result. Some account-available plugins can be used on mobile; desktop-only plugins cannot. Plugins are optional here. ChatGPT plugin guide.

Phone · Claude app

Open the Claude app, start a new chat, and paste the prompt. Ask for the requested result. Remote connectors are optional; local desktop extensions do not run on the phone. Claude connectors guide.

Windows

Open ChatGPT or Claude in a browser and paste the prompt. Alternatively, install one CLI in PowerShell using an official command below. These commands download and execute installers; check the linked vendor instructions first. Sign in when prompted; eligibility and plans vary. Use a folder you are comfortable granting the tool access to.

Codex CLI (official setup):

powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"
codex

Claude Code (official setup; an eligible paid or other supported account is required):

irm https://claude.ai/install.ps1 | iex
claude

Then paste the same prompt into the CLI. Review any access or changes it asks to make.

macOS

Open ChatGPT or Claude in a browser and paste the prompt. Alternatively, install one CLI in Terminal using an official command below. These commands download and execute installers; check the linked vendor instructions first. Sign in when prompted; eligibility and plans vary. Use a folder you are comfortable granting the tool access to.

Codex CLI (official setup):

curl -fsSL https://chatgpt.com/codex/install.sh | sh
codex

Claude Code (official setup; an eligible paid or other supported account is required):

curl -fsSL https://claude.ai/install.sh | bash
claude

Then paste the same prompt into the CLI. Review any access or changes it asks to make.

Linux

Open ChatGPT or Claude in a browser and paste the prompt. Alternatively, install one CLI in a terminal using an official command below. These commands download and execute installers; check the linked vendor instructions first. Sign in when prompted; eligibility and plans vary. Use a folder you are comfortable granting the tool access to.

Codex CLI (official setup):

curl -fsSL https://chatgpt.com/codex/install.sh | sh
codex

Claude Code (official setup; an eligible paid or other supported account is required):

curl -fsSL https://claude.ai/install.sh | bash
claude

Then paste the same prompt into the CLI. Review any access or changes it asks to make.

05 / Check and remix

Make sure it works for you

Check the arithmetic yourself: 20 ÷ 120 is about 16.7%, and 15 ÷ 100 is 15%.
Look for claims about why the numbers changed. The practice data does not establish a cause.
Ask the assistant to correct anything it cannot support and to separate facts from assumptions.
Remix with a small dataset you are allowed to share; keep private information out of the prompt.

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