create_assistant · Vapi MCP Server MCP: Risk & Policy

WHAT IT DOES

What create_assistant does on Vapi MCP Server

AI agents use create_assistant to create or update resources in Vapi MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Vapi MCP Server environment.

WHY IT NEEDS A POLICY

Why create_assistant needs a policy

This tool creates a new assistant resource, which is a reversible write operation. While not destructive (data can be deleted), it establishes a new voice AI assistant that could be configured to make calls or interact with users. Severity is high because a misconfigured or malicious assistant created through this tool could be used to make unwanted calls, impersonate entities, or perform social engineering at scale.

From the tool's definition Tool description states 'Creates a new Vapi assistant', which is a create operation that modifies state by adding a new resource to the Vapi platform.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_assistant Rate-limited

create_assistant stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "create_assistant": {
      "limits": [
        {
          "counter": "create_assistant_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about create_assistant

What does the create_assistant tool do? +

Creates a new Vapi assistant. It is categorised as a Write tool in the Vapi MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_assistant? +

Register the Vapi MCP Server MCP server in PolicyLayer and add a rule for create_assistant: 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 Vapi MCP Server. Nothing to install.

What risk level is create_assistant? +

create_assistant is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit create_assistant? +

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

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

create_assistant is provided by the Vapi MCP Server MCP server (kuchikirenji/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.