Building with a coding agent

Set up Claude Code, Cursor or Codex to build a Kustom Checkout integration — its own Playground API credentials, the Kustom skill and the Markdown it reads.

On this page you'll

Give an agent its own Playground API credentials, through the environment
Install a skill that teaches an agent the create → render → confirm flow
Point an agent at the Markdown it should read

This page is for you, the developer setting up a coding agent. The agent itself starts from /llms.txt and needs nothing here. What it can’t do on its own is get API credentials or install itself, so those two steps are yours, and then you tell it where to read.

Give the agent its own API credentials

The live demos on these pages run on a temporary Playground session meant for the browser, and there are no throwaway credentials for agents. An agent needs Playground API credentials of its own before its first call:

Sign up through the Playground onboarding form. It’s free and self-serve.
In the Playground Portal, go to Developers → API and click Generate new. A Merchant ID can carry several credentials, so give the agent its own and revoke it when you’re done.
Pass the API username and API password to the agent through the environment, not the prompt:

export KUSTOM_API_USERNAME=...                 # the Portal's Key ID
export KUSTOM_API_PASSWORD=kco_test_api_...
curl -s -X POST https://api.playground.kustom.co/checkout/v3/orders \
  -u "$KUSTOM_API_USERNAME:$KUSTOM_API_PASSWORD" -H 'Content-Type: application/json' \
  -d @order.json

A kco_test_ password only works against api.playground.kustom.co. Authentication covers both values and how to send them.

Install the skill

The skill teaches the create → render → confirm flow, and tells the agent to ask you for credentials before it makes a call. This installs it for Claude Code:

mkdir -p .claude/skills/kustom-checkout && curl -s https://docs.kustom.co/skill/SKILL.md -o .claude/skills/kustom-checkout/SKILL.md

For another agent, give it /skill/SKILL.md the way it takes project instructions.

Point it at the docs

Hand the agent /llms.txt first. It indexes every page with a one-line summary, and it carries the naming rules an agent gets wrong unprompted.

Every page also has a Markdown version at the same URL with .md appended, for example /checkout/integrate/create-order.md. To pass one page into a chat, use Copy page in its title.

Next steps

Checkout in 15 minutes — the flow the skill automates, run by hand.
Checkout API reference — the schemas an agent will need for anything beyond the defaults.

This page is also available as Markdown — append .md to its URL — and is indexed in llms.txt.