mcp-checkout-guard

Pre-purchase check for shops, payment links and paid APIs — a single-purpose MCP server for AI agents. No install, no account: it runs as a remote server; this repo also has a zero-dependency stdio bridge.

https://angel.oroboros-design.com/mcp/checkout-guard

Use it

Claude Code

claude mcp add --transport http checkout-guard https://angel.oroboros-design.com/mcp/checkout-guard

Claude Desktop, Cursor, Windsurf, VS Code (remote server)

{ "mcpServers": { "checkout-guard": { "url": "https://angel.oroboros-design.com/mcp/checkout-guard" } } }

Any stdio client (Node 18+)

{ "mcpServers": { "checkout-guard": { "command": "npx", "args": ["-y", "github:daoudandiaye98-alt/mcp-checkout-guard"] } } }

Then ask your agent, for example: Before paying at https://shop.example.com/checkout, run preflight and stop unless the verdict is pay.

Tools

Tool	Price	What it does
preflight	3 free calls per agent, then 0.25 USDC	One request to the url: TLS, domain age, look-alike domains, redirects to foreign gateways, payment provider, card fields in the page, http forms, text aimed at agents and, for x402, USDC contract, payTo, EIP-712 domain and price traps. Verdict pay, caution or do_not_pay with every reason.
buy_pack_with_card	—	Prepaid calls by card (Stripe) when the free calls are used up.

Paying

The first 3 paid calls per agent are free (identify your agent with the header X-API-Key, or set ANGEL_API_KEY for the stdio bridge). After that each call is paid per request in USDC on Base via x402 (params._meta["x402/payment"]), with a prepaid pack (bundle_token) or by card (buy_pack_with_card). The 402 answer names the exact amount and the pay-to address before anything is signed.

Disclosure: on verdict pay for a shop with an affiliate programme (for example Amazon), the answer can include a partner_link to the same merchant; Angel may earn a commission if you buy through it, the merchant sets the price, and the checked url is just as safe. Pass partner_link: false to leave it out.

More

• Same checks as a library: npm i angel-agent-guard · pip install angel-agent-guard (angel-agent-guard)
• All of Angel's tools in one server: https://angel.oroboros-design.com/agenten/signal/mcp · A2A agent card: https://angel.oroboros-design.com/.well-known/agent.json
• MCP Registry: com.oroboros-design.angel/checkout-guard

Operated by Oroboros Design (Köln, Germany). MIT licence for the code in this repo.