mpp-stripe-client

name	mpp-stripe-client
description	Machine Payment Protocol (MPP) client using Stripe. Prompts for a target MPP-protected URL, then handles the 402 challenge flow automatically — creating a Stripe Shared Payment Token (SPT) and retrying to retrieve the paid resource.
version	1.0.0
type	skill

MPP Stripe Client Skill

When to Use

• "Pay for this resource at ..."
• "Access this MPP-protected URL ..."
• "Use Stripe to pay for ..."
• "Run MPP client against ..."
• Any request referencing a URL that returns 402 Payment Required with an MPP challenge.

Prerequisites

The project must be installed at ~/Documents/Management/Development/mpp-stripe-client/:

cd ~/Documents/Management/Development/mpp-stripe-client
npm install

A Stripe test secret key (sk_test_...) is required. Set it as an environment variable:

export STRIPE_SECRET_KEY=sk_test_...

Or the skill will ask for it.

Workflow

⛔ PRE-BUILD CHECK: Before producing output, re-read the relevant workflow section above and re-read any checklists or verification gates defined in this skill. Confirm each checklist item before writing output. Build to pass — do not retro-fit. Apply the CLAUDE.md Anti-Drift Protocol: re-read spec section before build, gate-first validation, section-by-section delivery.

Step 1 — Collect target URL and Stripe key

Ask the user for:

1. Target URL — the MPP-protected resource to access
2. Stripe secret key — if STRIPE_SECRET_KEY is not already in the environment

If no URL is provided, ask for it. Do not assume defaults.

Step 2 — Run the MPP client

With the target URL and Stripe key confirmed, execute the client. The client runs from the installed project directory and accepts the target URL as SERVER_URL:

cd ~/Documents/Management/Development/mpp-stripe-client \
  && SERVER_URL="<target-url>" STRIPE_SECRET_KEY="<key>" npx tsx cli.ts

Do not use npm run cli — it reads .env which overrides inline variables with localhost defaults. Always invoke npx tsx cli.ts directly with inline SERVER_URL and STRIPE_SECRET_KEY.

The client will:

1. GET <target-url> — receive 402 Payment Required with challenge
2. Create a Stripe test payment method
3. Create a Stripe Shared Payment Token (SPT) scoped to the challenge amount
4. GET <target-url> with Authorization: Payment <credential>
5. Receive 200 with the paid resource and receipt

Step 3 — Present the result

Show the user:

• The HTTP status
• The response body (the paid resource)
• The receipt header value (Authentication-Info)

Error handling

• If the server doesn't return 402, report the actual status and body.
• If Stripe calls fail, report the Stripe error message.
• If the MPP challenge parsing fails, report the raw challenge for diagnosis.

Configuration

Variable	Required	Default
STRIPE_SECRET_KEY	Yes	Prompted if missing
SERVER_URL	Yes	Prompted if missing
STRIPE_PAYMENT_METHOD	No	Creates test card pm_...
MPPX_STRIPE_SPT_URL	No	Stripe test endpoint