partial_refund

THE RISK

Critical Risk

Why partial_refund needs a policy

This tool commits a financial obligation (refund) that moves money. Even though it is reversible (a refund can theoretically be reversed via a chargeback or counter-refund), it represents a direct monetary transaction.

From the tool's definition Tool name 'partial_refund' and description 'Refund a portion of a charge' explicitly indicate movement of money back to a customer. The server context 'AP2 — Google's Agent-to-Agent Payment Protocol' confirms this operates in a payment system.

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

POLICY

How to control partial_refund

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 partial_refund:

policy.json

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

Any call to partial_refund 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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All 1300 Mcp Ap2 tools →

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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 partial_refund

What does the partial_refund tool do? +

Refund a portion of a charge (explicit partial refund; returns amount in cents). 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 partial_refund? +

Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for partial_refund: 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 partial_refund? +

partial_refund 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 partial_refund? +

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

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

partial_refund 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.

CHECK YOUR STACK →