create_tool · Vapi MCP Server MCP: Risk & Policy

WHAT IT DOES

What create_tool does on Vapi MCP Server

AI agents use create_tool 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_tool needs a policy

This tool creates new tools within the Vapi voice AI system. It is a reversible write operation (new tools can be deleted or modified later), not a destructive action. The severity is medium because creating tools could potentially enable unintended voice AI behaviors if misconfigured, but the operation itself is not irreversible and does not directly execute code or move money.

From the tool's definition Tool name 'create_tool' and description 'Creates a new Vapi tool' indicate a create operation that adds new data/configuration to the Vapi platform.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_tool Rate-limited

create_tool 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_tool": {
      "limits": [
        {
          "counter": "create_tool_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_tool

What does the create_tool tool do? +

Creates a new Vapi tool. 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_tool? +

Register the Vapi MCP Server MCP server in PolicyLayer and add a rule for create_tool: 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_tool? +

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

Can I rate-limit create_tool? +

Yes. Add a rate_limit block to the create_tool 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_tool completely? +

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

create_tool 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.