retell_register_phone_call · Retell AI MCP Server MCP

WHAT IT DOES

What retell_register_phone_call does on Retell AI MCP Server

AI agents invoke retell_register_phone_call to trigger actions in Retell AI 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 retell_register_phone_call needs a policy

This tool triggers an external telephony operation — registering/initiating an inbound call — which causes real-world side effects beyond simple data creation. It interacts with live phone infrastructure and could result in active voice calls being established. This goes beyond a Write (data creation) into Execute territory since it triggers external operational processes in a telephony system.

From the tool's definition Register an inbound call from a custom telephony provider

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

retell_register_phone_call Rate-limited

retell_register_phone_call 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": {
    "retell_register_phone_call": {
      "limits": [
        {
          "counter": "retell_register_phone_call_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 Retell AI MCP Server, so you can run agents against it safely.

FAQ

Questions about retell_register_phone_call

What does the retell_register_phone_call tool do? +

Register an inbound call from a custom telephony provider. It is categorised as a Execute tool in the Retell AI 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 retell_register_phone_call? +

Register the Retell AI MCP Server MCP server in PolicyLayer and add a rule for retell_register_phone_call: 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 Retell AI MCP Server. Nothing to install.

What risk level is retell_register_phone_call? +

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

Can I rate-limit retell_register_phone_call? +

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

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

retell_register_phone_call is provided by the Retell AI MCP Server MCP server (itsanamune/retellsimp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.