update_payment_link

THE RISK

Critical Risk

Why update_payment_link needs a policy

This tool modifies payment links within Google's Agent-to-Agent Payment Protocol. Changing a payment link can redirect funds, alter payment amounts, or modify recipient details, making it a Financial category tool. Misuse could result in fraudulent payment redirection or financial loss.

From the tool's definition 'update_payment_link' and 'Update a payment link' — modifying a payment link in a payment protocol (AP2) directly affects financial transaction flows

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

POLICY

How to control update_payment_link

PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Ap2, and nothing reaches the server without passing your rules. This is the rule we recommend for update_payment_link:

policy.json

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

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

Create a free account and register Mcp Ap2 — 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

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Go deeper

Critical-risk tools in Mcp Ap2 → 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 update_payment_link

What does the update_payment_link tool do? +

Update a payment link. It is categorised as a Financial tool in the Mcp Ap2 MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on update_payment_link? +

Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for update_payment_link: 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 Mcp Ap2. Nothing to install.

What risk level is update_payment_link? +

update_payment_link 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 update_payment_link? +

Yes. Add a rate_limit block to the update_payment_link 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 update_payment_link completely? +

Set action: deny in the PolicyLayer policy for update_payment_link. 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 update_payment_link? +

update_payment_link is provided by the Mcp Ap2 MCP server (@codespar/mcp-ap2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mcp Ap2 tool call.

Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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