lookup_phone

THE RISK

Low Risk

Why lookup_phone needs a policy

This tool retrieves and validates phone number information without creating, modifying, deleting, or executing operations. It performs a read-only lookup operation. The 'Optional' note reinforces its auxiliary nature. Severity is low because phone number validation has minimal blast radius—it cannot modify data, trigger financial transactions, or cause destructive outcomes even if misused.

From the tool's definition Tool name 'lookup_phone' and description 'Validate and normalize a phone number via Lookups v2' indicate a query/validation operation with no data modification or external side effects.

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

POLICY

How to control lookup_phone

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

policy.json

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

lookup_phone 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 Afip — 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

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 lookup_phone

What does the lookup_phone tool do? +

Validate and normalize a phone number via Lookups v2. Optional. It is categorised as a Read tool in the Mcp Afip MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on lookup_phone? +

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

What risk level is lookup_phone? +

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

Can I rate-limit lookup_phone? +

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

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

lookup_phone is provided by the Mcp Afip MCP server (codespar/mcp-dev-latam). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mcp Afip tool call.

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

CHECK YOUR STACK →