buy_phone_number

THE RISK

Critical Risk

Why buy_phone_number needs a policy

Provisioning a phone number typically involves a recurring or one-time financial commitment (subscription or purchase). Despite being on an AFIP/invoicing server (possibly a mismatch), the action itself commits financial resources. Financial > all other categories by severity rules.

From the tool's definition buy_phone_number — 'Provision a new phone number' implies purchasing/acquiring a phone number, which incurs a financial cost/obligation

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

POLICY

How to control buy_phone_number

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 buy_phone_number:

policy.json

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

Any call to buy_phone_number is blocked until a human approves it. The rest of the server keeps working.

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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 Afip tools →

Financial tools on other servers

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Go deeper

Critical-risk tools in Mcp Afip → 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 buy_phone_number

What does the buy_phone_number tool do? +

Provision a new phone number. Supply either a specific. It is categorised as a Financial tool in the Mcp Afip MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on buy_phone_number? +

Register the Mcp Afip MCP server in PolicyLayer and add a rule for buy_phone_number: 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 buy_phone_number? +

buy_phone_number 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 buy_phone_number? +

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

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

buy_phone_number 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 →