UCP Project Setup

Before writing any code

1. Web-search site:ucp.dev specification overview to confirm the latest spec version.
2. Fetch the latest SDK READMEs:
   • Python: https://github.com/Universal-Commerce-Protocol/python-sdk
   • JS/TS: https://github.com/Universal-Commerce-Protocol/js-sdk
3. Fetch the sample servers for reference architecture:
   • https://github.com/Universal-Commerce-Protocol/samples

What to scaffold

1. Determine the role

Ask the user: are they building a Business (merchant server that exposes checkout), a Platform (AI agent that drives checkout), or both?

2. Install the SDK

• Python: Clone the official python-sdk repo and use uv sync, or install FastUCP via pip install fastucp-python for decorator-based approach. Note: fastucp-python is a community/third-party package, not an official UCP SDK.
• JS/TS: npm install @ucp-js/sdk for TypeScript types and Zod schemas.
• Always verify the latest install instructions from the live GitHub README before running.

3. Discovery profile (/.well-known/ucp)

Every Business MUST publish a discovery profile. This is the first thing to implement.

The profile declares:

• Protocol version
• Services (which transport bindings are supported, with endpoint URLs)
• Capabilities (checkout, orders, identity linking — each with version and schema URI)
• Extensions (fulfillment, discount, buyer consent, AP2 — each declaring which capability they extend)
• Payment handlers (accepted payment methods with configuration)
• Signing keys (EC P-256 public keys for webhook signatures)

Fetch https://ucp.dev/specification/overview/ and https://developers.google.com/merchant/ucp/guides/ucp-profile for the exact current schema before generating the profile.

4. Project structure (Business server)

my-ucp-server/
├── app/
│   ├── main.py (or index.ts)         # Server entrypoint
│   ├── discovery.py                   # /.well-known/ucp endpoint
│   ├── checkout/
│   │   ├── routes.py                  # Checkout CRUD + complete + cancel
│   │   ├── models.py                  # Checkout data models (from SDK)
│   │   └── negotiation.py            # Capability negotiation logic
│   ├── orders/
│   │   ├── routes.py                  # Order management
│   │   ├── webhooks.py               # Webhook delivery + signing
│   │   └── models.py
│   ├── payments/
│   │   ├── handlers.py               # Payment handler configuration
│   │   └── processing.py             # Credential processing
│   ├── fulfillment/
│   │   └── routes.py                 # Fulfillment extension logic
│   └── common/
│       ├── headers.py                # UCP-Agent, Idempotency-Key parsing
│       ├── errors.py                 # UCP error/message model
│       └── crypto.py                # JWT signing for webhooks
├── tests/
│   └── conformance/                  # Conformance test runner
├── .well-known/
│   └── ucp (or served dynamically)
├── .env                              # API keys, signing key paths
└── pyproject.toml (or package.json)

5. Environment configuration

• Store signing private keys securely (env vars or secrets manager)
• Never hardcode payment handler credentials
• Use .env + .gitignore for all secrets

6. Verify setup

• Serve the discovery profile and validate its JSON against the schema from https://ucp.dev/specification/reference/
• Use the UCP Playground at https://ucp.dev/playground/ to test discovery step