# Thesagarjain9 Cpu Ucp Onboard Ucp Checkout > UCP Checkout API Generator - Skill: `tomevault-io/thesagarjain9-cpu-ucp-onboard-ucp-checkout` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/thesagarjain9-cpu-ucp-onboard-ucp-checkout` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/thesagarjain9-cpu-ucp-onboard-ucp-checkout/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Integrations & APIs - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/thesagarjain9-cpu-ucp-onboard-ucp-checkout --- # UCP Checkout API Generator Generate a deployable checkout API that implements UCP shopping capabilities. ## Prerequisites - `store/clients/{client_name}/ucp-profile.json` must exist (from ucp-profile) - `store/clients/{client_name}/catalog.json` must exist (from ucp-catalog) - Merchant must specify: tech stack, hosting environment, payment provider credentials ## Step 1: Select Template | Stack | Framework | Why | |-------|-----------|-----| | `node` | Express.js | Most common for Shopify ecosystem | | `python` | FastAPI | Best for data-heavy catalogs, async support | | `php` | Laravel | Most common for WooCommerce ecosystem | ## Step 2: Generate Project Structure ### Node.js (Express) ``` ucp-server/ ├── package.json ├── .env.example ├── src/ │ ├── index.js — Server entry, routes │ ├── middleware/ │ │ └── ucp-negotiation.js — Capability negotiation │ ├── routes/ │ │ ├── checkout.js — create/update/retrieve/complete/cancel │ │ ├── catalog.js — search/lookup │ │ └── well-known.js — /.well-known/ucp static serve │ ├── services/ │ │ ├── session-store.js — In-memory session (swap for Redis in prod) │ │ ├── catalog-service.js — Product data access │ │ ├── totals.js — Price calculation engine │ │ └── payment.js — Payment handler integration │ └── schemas/ │ └── ucp-profile.json — The merchant's profile (from ucp-profile skill) └── README.md ``` ### Python (FastAPI) ``` ucp-server/ ├── requirements.txt ├── .env.example ├── app/ │ ├── main.py — FastAPI app, routes │ ├── middleware/ │ │ └── negotiation.py │ ├── routers/ │ │ ├── checkout.py │ │ ├── catalog.py │ │ └── well_known.py │ ├── services/ │ │ ├── session_store.py │ │ ├── catalog_service.py │ │ ├── totals.py │ │ └── payment.py │ └── schemas/ │ └── ucp_profile.json └── README.md ``` ## Step 3: Implement Core Logic ### 3.1 Capability Negotiation Every checkout response must include `ucp` metadata with active capabilities: ```python def negotiate(platform_profile, business_profile): """Compute capability intersection between platform and business.""" platform_caps = set(platform_profile.get("capabilities", {}).keys()) business_caps = set(business_profile["capabilities"].keys()) active = platform_caps & business_caps # Prune orphaned extensions for cap_name, cap_def in business_profile["capabilities"].items(): if "extends" in cap_def[0]: parent = cap_def[0]["extends"] if parent not in active: active.discard(cap_name) return {name: business_profile["capabilities"][name] for name in active} ``` ### 3.2 Checkout Session Lifecycle ``` POST /ucp/v1/checkout → create session → status: "incomplete" → returns: id, line_items, totals, status, links POST /ucp/v1/checkout/{id} → update session → recalculate totals → status remains "incomplete" or moves to "requires_escalation" GET /ucp/v1/checkout/{id} → retrieve session → return current state POST /ucp/v1/checkout/{id}/complete → complete session → validate payment instrument → charge via payment handler → status: "complete_in_progress" → "completed" POST /ucp/v1/checkout/{id}/cancel → cancel session → status: "canceled" ``` ### 3.3 Totals Calculation ```python def calculate_totals(line_items, discounts=None, fulfillment=None, tax_rate=0): subtotal = sum(item["item"]["price"]["amount"] * item["quantity"] for item in line_items) totals = [ {"type": "subtotal", "amount": subtotal} ] if discounts: discount_amount = calculate_discounts(discounts, subtotal) totals.append({"type": "discount", "amount": -abs(discount_amount)}) subtotal -= abs(discount_amount) if fulfillment: shipping = fulfillment["cost"]["amount"] totals.append({"type": "fulfillment", "amount": shipping}) subtotal += shipping if tax_rate > 0: tax = round(subtotal * tax_rate) totals.append({"type": "tax", "amount": tax}) subtotal += tax totals.append({"type": "total", "amount": subtotal}) return totals ``` > **HARD RULE — Totals must always contain exactly one `subtotal` and one `total`.** Discount amounts must be negative. All other amounts must be >= 0. Amounts are integers in minor units. ### 3.4 Line Items from Catalog ```python def build_line_item(product_id, variant_id, quantity, catalog): product = catalog.find_product(product_id) variant = catalog.find_variant(product_id, variant_id) return { "id": f"li_{variant_id}", "item": { "id": variant_id, "title": variant["title"], "price": variant["price"] }, "quantity": quantity, "totals": [ {"type": "subtotal", "amount": variant["price"]["amount"] * quantity}, {"type": "total", "amount": variant["price"]["amount"] * quantity} ] } ``` ### 3.5 Response Structure Every checkout response must include: ```json { "ucp": { "version": "2026-01-23", "capabilities": {}, "payment_handlers": {} }, "id": "session_xxx", "status": "incomplete", "currency": "USD", "line_items": [], "totals": [ {"type": "subtotal", "amount": 2999, "display_text": "$29.99"}, {"type": "total", "amount": 2999, "display_text": "$29.99"} ], "links": [ {"type": "privacy_policy", "url": "https://example.com/privacy"}, {"type": "terms_of_service", "url": "https://example.com/tos"} ] } ``` ## Step 4: Generate .env Template ``` # UCP Server Configuration PORT=3000 MERCHANT_DOMAIN=example.com # Payment Provider (Stripe example) STRIPE_SECRET_KEY=sk_test_xxx STRIPE_PUBLISHABLE_KEY=pk_test_xxx # Product Data Source CATALOG_SOURCE=shopify SHOPIFY_STORE_URL=https://example.myshopify.com # Session Storage (production) REDIS_URL=redis://localhost:6379 ``` ## Step 5: Output Save to `store/clients/{client_name}/`: - `ucp-server/` — complete deployable project - `api-docs.md` — endpoint documentation - `deploy-guide.md` — hosting instructions (Vercel, Railway, VPS) ## Scripts | Script | Purpose | Dependencies | |--------|---------|-------------| | `generate_api.py` | Code generator using Jinja2 templates | jinja2, json | ## Templates Located in `templates/`: - `node/` — Express.js project template - `python/` — FastAPI project template - `php/` — Laravel project template ## Collaboration ``` ucp-profile → (ucp-profile.json) ──┐ ├── ucp-checkout (this skill) ucp-catalog → (catalog.json) ──────┘ │ ├── outputs → ucp-server/ (deployable code) ├── outputs → api-docs.md ├── outputs → deploy-guide.md │ └── verified by → ucp-validate ``` --- > Source: [thesagarjain9-cpu/ucp-onboard](https://github.com/thesagarjain9-cpu/ucp-onboard) — distributed by [TomeVault](https://tomevault.io).