backchannel_resend_otp

THE RISK

High Risk

Why backchannel_resend_otp needs a policy

This tool triggers an external operation — sending an OTP message to a shopper — which is a side-effectful action (dispatching a communication/authentication code) rather than a simple read or data write. It doesn't move money or irreversibly destroy data, but it does execute an outbound action with real-world effects (OTP delivery) tied to an authorization flow.

From the tool's definition Resend the OTP to the shopper for an in-flight authorization ticket

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

POLICY

How to control backchannel_resend_otp

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 backchannel_resend_otp:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "backchannel_resend_otp": {
      "limits": [
        {
          "counter": "backchannel_resend_otp_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

backchannel_resend_otp stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. 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.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

High-risk tools in Mcp Ap2 → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-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.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about backchannel_resend_otp

What does the backchannel_resend_otp tool do? +

Resend the OTP to the shopper for an in-flight authorization ticket. It is categorised as a Execute tool in the Mcp Ap2 MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on backchannel_resend_otp? +

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

backchannel_resend_otp is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit backchannel_resend_otp? +

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

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

backchannel_resend_otp 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 →