Checkout Guard — pre-purchase check for shops, payment links and paid APIs

com.oroboros-design.angelPublished by angel.oroboros-design.comOfficial publisherv1.0.0Updated Nov 14, 2026

Pre-purchase check for any shop, checkout or payment link, paid API or x402 endpoint.

The publisher's own server: Agent safety checks: prompt-injection scan, honeypot check, x402 preflight + crypto data (USDC/x402)

VerifiedStreamable HTTPWeb executableFinanceSecurity & Monitoring

Overview

AI-generated overview

Remote MCP server that runs a pre-purchase safety check on a shop, checkout or payment link, paid API or x402 endpoint and returns a pay, caution or…

What you can do
  • Run a preflight check on a URL before an agent pays or calls it: TLS, domain age, look-alike domains, redirects to foreign gateways, payment provider, card fields, forms and text aimed at agents
  • Inspect x402 endpoints for USDC contract, payTo address, EIP-712 domain and price traps
  • Get a verdict of pay, caution or do_not_pay with the reasons behind it
  • Buy prepaid call packs by card in EUR when the free calls are used up
When to use it
Use it when an agent is about to pay at an unfamiliar shop, follow a payment link, or call an unknown paid API or x402 endpoint and you want a second opinion before money moves.
Requirements
Remote HTTP endpoint, no install or account. An optional X-API-Key header (or ANGEL_API_KEY for the stdio bridge) identifies the agent for the 3 free calls. After that, calls are paid in USDC on Base via x402, with a prepaid bundle token, or by card through buy_pack_with_card. A Node 18+ stdio bridge is offered for clients that need one.
Before you install
The service is paid after 3 free calls per agent; payments are made in USDC on Base or by card, so real money is involved. On a pay verdict the answer may include an affiliate partner_link the operator earns commission on unless partner_link is set to false. The URL being checked is sent to a third-party server.

Installation

In SourceWeft

  1. Open Checkout Guard — pre-purchase check for shops, payment links and paid APIs in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/com.oroboros-design.angel%2Fcheckout-guard/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "checkout-guard-pre-purchase-check-for-sh": {
      "type": "http",
      "url": "https://angel.oroboros-design.com/mcp/checkout-guard"
    }
  }
}

README

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

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

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

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

Any stdio client (Node 18+)

json
{ "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

ToolPriceWhat it does
preflight3 free calls per agent, then 0.25 USDCOne 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.

Source: README.md at commit f1d563b

Tools

2

preflight

Pre-purchase check for any shop, checkout link, payment page, API or x402 endpoint

Before an agent buys, pays or calls an unknown endpoint: one unpaid request to any https shop, checkout or payment link (Stripe, Shopify, PayPal and others), API or x402 endpoint. Checks TLS, domain age, look-alike domains, redirects to foreign gateways, the payment provider, card fields in the page, http forms, text aimed at agents in the page and, for x402, USDC contract, payTo, EIP-712 domain and price traps. Verdict pay, caution or do_not_pay, risk_score, merchant_signals. 0.25 USDC base (new payers 0.25, >10 payments 0.175; 5 pack calls). After: input-guard on the page text you will act on, gas-window before you settle on Base (the result's next field has the exact call).

Parametersurlrequiredmethodpayment_txbundle_tokenpartner_linkmax_price_usdpayer_address

buy_pack_with_card

TradeSignal: pack by card

For agents and people without USDC: prepaid packs paid in EUR by card or Link (100 calls €5.00 · 500 calls €25.00 · 5,000 calls €199.00) — including Link's wallet for agents (one-time card, approved by the human). Returns checkout_url; after payment the success page (Accept: application/json) returns the bundle_token, and it is e-mailed. After: get_signals with bundle_token.

Parameterscallsemail

Version history

1
  1. v1.0.0LatestNov 14, 2026

Score

100% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listedRequired15 pts
  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts

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