void_sale

THE RISK

Critical Risk

Why void_sale needs a policy

Voiding a sale is a direct financial action that cancels or reverses a payment transaction, which can result in significant monetary impact. It falls squarely in the Financial category as it modifies financial obligations. The blast radius is critical because an AI agent misusing this tool could cancel legitimate sales transactions, causing revenue loss and potential disputes.

From the tool's definition 'Void / cancel a sale' and 'PUT /sales/{paymentId}/void' — this reverses or cancels a financial transaction, committing a financial operation that affects payment obligations

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

POLICY

How to control void_sale

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 void_sale:

policy.json

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

Any call to void_sale 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

Related tools and policies

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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 void_sale

What does the void_sale tool do? +

Void / cancel a sale (PUT /sales/{paymentId}/void). Supports full void (omit amount) or partial void. 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 void_sale? +

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

void_sale 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 void_sale? +

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

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

void_sale 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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