ucp_checkout_complete

THE RISK

Critical Risk

Why ucp_checkout_complete needs a policy

The tool name 'ucp_checkout_complete' strongly implies finalizing a purchase/payment transaction. Given the server's explicit purpose of handling payments and checkout at merchants, completing a checkout is a financial commitment. The description is empty, so confidence is slightly reduced, but the context from the server description and sibling tools makes the financial classification highly probable.

From the tool's definition Tool name 'ucp_checkout_complete' on a server described as handling 'checkout' and 'payment' for shopping at merchants. Sibling tools include ucp_checkout_create, ucp_checkout_set_fulfillment, ucp_checkout_update.

Documented attack patterns abuse exactly the kind of access ucp_checkout_complete gives an agent:

POLICY

How to control ucp_checkout_complete

PolicyLayer is an MCP gateway — it sits between your AI agents and Ucp, and nothing reaches the server without passing your rules. This is the rule we recommend for ucp_checkout_complete:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "ucp_checkout_complete": {
      "deny_if": [
        {
          "conditions": [],
          "on_deny": "Requires human approval."
        }
      ]
    }
  }
}

Any call to ucp_checkout_complete is blocked until a human approves it. The rest of the server keeps working.

Create a free account and register Ucp — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

Related tools and policies

More Ucp tools

Financial ucp_checkout_create ucp_checkout_create Financial ucp_checkout_update ucp_checkout_update Write ucp_checkout_set_fulfillment ucp_checkout_set_fulfillment Read ucp_discover ucp_discover

All 5 Ucp tools →

Financial tools on other servers

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Go deeper

Critical-risk tools in Ucp → Every critical-risk tool this server exposes, in one view.
All critical-risk MCP tools → Every critical-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Human-in-the-loop → When a tool call should wait for a person — and when policy can decide alone.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
How to Add Spending Controls to Any MCP Agent →
Rate Limiting MCP Tool Calls: A Practical Guide →

FAQ

Questions about ucp_checkout_complete

What does the ucp_checkout_complete tool do? +

ucp_checkout_complete. It is categorised as a Financial tool in the Ucp MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on ucp_checkout_complete? +

Register the Ucp MCP server in PolicyLayer and add a rule for ucp_checkout_complete: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Ucp. Nothing to install.

What risk level is ucp_checkout_complete? +

ucp_checkout_complete is a Financial tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.

Can I rate-limit ucp_checkout_complete? +

Yes. Add a rate_limit block to the ucp_checkout_complete rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block ucp_checkout_complete completely? +

Set action: deny in the PolicyLayer policy for ucp_checkout_complete. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides ucp_checkout_complete? +

ucp_checkout_complete is provided by the Ucp MCP server (nguthrie/ucp-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Ucp tool call.

Start from Ucp, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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