Courier

Courier gives your AI agents an ID. PayPal verifies you, you add one connector to Claude, and then each thing you ask for is an errand with its own budget ("flowers on Floor Dash, about $20"), at any shop that accepts Courier. Limits are enforced in code. Shops see a verified agent and its limits, not your name.

It's standard MCP and OAuth 2.1, so Claude connects with no custom client.

New here? Start with the Quickstart: the story of one purchase, what works today and what's next.

Try it

You need Node 24 or newer. No keys or accounts are required.

git clone https://github.com/Djbrl/courier.git
cd courier
npm install
npm run demo

Open http://localhost:4000 and click Try the demo. Demo mode uses a clearly labelled PayPal simulator, so no real accounts are involved.

To try the real flow with your own Claude and PayPal's test environment, use the hosted site. To test your own code changes that way, follow the local setup.

Related MCP server: Allowance MCP

What it does

• Limits live in code. Budget, per-item limit, shop and expiry are enforced before any model runs.

• Only you set the budget. You type it in the chat or on Courier. The model can fill in the number, but can't confirm it.

• Call it back any time. Revoking takes effect in seconds. Claude stays connected, ready for the next ticket, and you can remove your saved PayPal in Settings.

Try to break it. Release the bots fires eight real attacks at the shop, including forged IDs, stolen tokens, overspending and prompt injection. They also run on every commit.

How it works

flowchart LR
    Person([You]) -- "write the ticket" --> Courier
    Agent[Claude] -- "OAuth 2.1" --> Courier
    Agent -- "MCP + signed ID" --> Shop
    Shop -- "may it spend this?" --> Courier
    Courier -- "verify, pay" --> PayPal

apps/courier      The authorization server, spend limits and your app
apps/store        Five demo shops, each with its own MCP server
packages/shared   PayPal gateway, intent check, visa model, design system
tests             Unit tests, an end-to-end run, an official MCP client check

Docs

• Quickstart: what Courier does, what works today and what's next

• Code walkthrough: follow one purchase through the code, in about 15 minutes

• Architecture: the flows, the decisions and a glossary

• Live test: run it with the real PayPal sandbox and real Claude

• Contributing and Security

Status

Courier is a prototype. It only handles sandbox and simulated money.

• Working with real Claude and the PayPal sandbox: connecting, the ticket, paying through a PayPal link and paying with saved PayPal.

• Built and tested on the simulator, not yet on the sandbox: the $5 bond.

• Next: Runs, where several people's couriers buy one thing together.

License

MIT