verify_otp · Nubra MCP Server MCP: Risk & Policy

WHAT IT DOES

What verify_otp does on Nubra MCP Server

AI agents invoke verify_otp to trigger actions in Nubra MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why verify_otp needs a policy

This tool triggers an authentication step in an external trading platform, completing part of a multi-factor login flow. It causes a state change on the server (session/token creation) and chains into further privileged operations (MPIN verification, then full platform access). This is an external operation with significant consequences if misused — granting unauthorized access to a financial trading account.

From the tool's definition Verify the OTP for the current environment. If successful, ask for MPIN and call verify_mpin next.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

verify_otp Rate-limited

verify_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.

View as policy code

policy.json

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

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Nubra MCP Server, so you can run agents against it safely.

FAQ

Questions about verify_otp

What does the verify_otp tool do? +

Verify the OTP for the current environment. If successful, ask for MPIN and call verify_mpin next. It is categorised as a Execute tool in the Nubra MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on verify_otp? +

Register the Nubra MCP Server MCP server in PolicyLayer and add a rule for verify_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 Nubra MCP Server. Nothing to install.

What risk level is verify_otp? +

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

Can I rate-limit verify_otp? +

Yes. Add a rate_limit block to the verify_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 verify_otp completely? +

Set action: deny in the PolicyLayer policy for verify_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 verify_otp? +

verify_otp is provided by the Nubra MCP Server MCP server (socials-zanskar/nubra-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.