list_postal_codes

THE RISK

Low Risk

Why list_postal_codes needs a policy

This tool retrieves public postal code data based on address search criteria. It does not create, modify, delete, execute code, or commit financial transactions. Despite being on a payment protocol server, this specific tool only reads address information, making it a Read category risk with low severity.

From the tool's definition Tool description states "Search addresses by street name or location (returns matching CEPs)" — a pure query/retrieval operation with no modification or side effects. The verb "Search" and return of postal codes confirms read-only behavior.

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

POLICY

How to control list_postal_codes

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 list_postal_codes:

policy.json

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

list_postal_codes 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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Read tools on other servers

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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 list_postal_codes

What does the list_postal_codes tool do? +

Search addresses by street name or location (returns matching CEPs). 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 list_postal_codes? +

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

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

Can I rate-limit list_postal_codes? +

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

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

list_postal_codes 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 →