| name | ucp-checkout-mcp |
| description | Implement UCP Checkout over the MCP (Model Context Protocol) binding — expose checkout operations as MCP tools for AI agents. Use when building an MCP server that AI agents like Claude or Gemini can call for commerce, or when integrating with Shopify's MCP endpoint. |
| allowed-tools | Read, Write, Edit, Bash, Grep, Glob, WebSearch, WebFetch |
UCP Checkout — MCP Binding
Before writing code
Fetch live spec: Web-search site:ucp.dev specification checkout-mcp and fetch the page for exact tool definitions, JSON-RPC envelope format, and _meta requirements.
For Shopify's production MCP server, fetch https://shopify.dev/docs/agents/checkout/mcp for auth flow and endpoint details.
Conceptual Architecture
How MCP Maps to UCP
UCP over MCP is a 1:1 mapping of checkout operations to MCP tools using JSON-RPC 2.0. The same data model as REST, different envelope.
Five MCP Tools
| MCP Tool Name | Maps To | Key Inputs |
|---|
create_checkout | POST /checkout-sessions | checkout object + idempotency_key |
get_checkout | GET /checkout-sessions/{id} | id |
update_checkout | PUT /checkout-sessions/{id} | id + checkout object |
complete_checkout | POST .../complete | id + payment_data + idempotency_key |
cancel_checkout | POST .../cancel | id + idempotency_key |
Meta Requirements
Every MCP tool call MUST include _meta.ucp.profile pointing to the platform's UCP profile URI. This replaces the UCP-Agent HTTP header from the REST binding.
Error Mapping
UCP errors embed inside JSON-RPC 2.0 error responses:
- JSON-RPC
error.code: -32603 (Internal Error)
- JSON-RPC
error.data: Contains an errors[] array, where each error has code, message, severity, and details fields
When to Use MCP Binding
- You're building a merchant MCP server that AI agents (Claude, Gemini, etc.) call via tool use
- You're integrating with an existing MCP server (e.g., Shopify's)
- You want AI agents to autonomously browse and purchase without REST client code
Implementation Guidance
Building a Business MCP Server:
- Implement the 5 tools using your MCP framework (e.g.,
@modelcontextprotocol/sdk for Node, mcp for Python)
- Extract
_meta.ucp.profile from every tool call for negotiation
- Return checkout objects as JSON in the MCP tool result
- Return errors using JSON-RPC error format with UCP data payload
- Implement idempotency on create and complete tools
Connecting to an existing MCP server (e.g., Shopify):
- Authenticate (Shopify uses OAuth2 client_credentials for access tokens)
- Connect to the MCP endpoint
- Call tools with proper
_meta.ucp.profile and checkout payloads
- Parse tool results for checkout status and messages
Shopify MCP Integration
Shopify provides a production MCP server for UCP checkout. Before implementing:
- Fetch https://shopify.dev/docs/agents/checkout/mcp for the latest auth flow, endpoint URL format, and error codes
- Authentication uses
POST https://api.shopify.com/auth/access_token with client credentials
- MCP endpoint is
POST https://{shop-domain}/api/ucp/mcp
