query_payment_by_merchant_code

THE RISK

Low Risk

Why query_payment_by_merchant_code needs a policy

This is a Read operation: it retrieves payment information by merchant code without creating, modifying, or deleting anything. Severity is medium rather than low because payment details are sensitive and could enable fraud if exposed to an unauthorized agent, but the tool itself performs no financial transaction or destructive action.

From the tool's definition Tool name contains 'query' and description states 'Get payment details' — retrieves data without modification. However, payment details are sensitive financial data (merchant codes, transaction records).

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

POLICY

How to control query_payment_by_merchant_code

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 query_payment_by_merchant_code:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "query_payment_by_merchant_code": {}
  }
}

query_payment_by_merchant_code is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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.

CAP THIS TOOL →

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EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about query_payment_by_merchant_code

What does the query_payment_by_merchant_code tool do? +

Get payment details by merchant_payment_code (alternative to hash). It is categorised as a Read tool in the Mcp Ap2 MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on query_payment_by_merchant_code? +

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

query_payment_by_merchant_code is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit query_payment_by_merchant_code? +

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

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

query_payment_by_merchant_code 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 →