vapi_update_assistant · Mcp Vapi MCP: Risk & Policy

WHAT IT DOES

What vapi_update_assistant does on Mcp Vapi

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

WHY IT NEEDS A POLICY

Why vapi_update_assistant needs a policy

The tool modifies existing data (assistant configuration) in a reversible manner. While 'update' could theoretically span Write or Execute depending on what assistant configuration changes trigger, the description indicates a standard partial update of resource properties rather than triggering code execution or external operations.

From the tool's definition Tool name contains 'update' and description explicitly states 'Update an existing assistant (partial update — only send the fields you want to change).' This is a modification operation on an existing resource.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

vapi_update_assistant Rate-limited

vapi_update_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": {
    "vapi_update_assistant": {
      "limits": [
        {
          "counter": "vapi_update_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 Mcp Vapi, so you can run agents against it safely.

FAQ

Questions about vapi_update_assistant

What does the vapi_update_assistant tool do? +

Update an existing assistant (partial update — only send the fields you want to change). It is categorised as a Write tool in the Mcp Vapi MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on vapi_update_assistant? +

Register the Mcp Vapi MCP server in PolicyLayer and add a rule for vapi_update_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 Mcp Vapi. Nothing to install.

What risk level is vapi_update_assistant? +

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

Can I rate-limit vapi_update_assistant? +

Yes. Add a rate_limit block to the vapi_update_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 vapi_update_assistant completely? +

Set action: deny in the PolicyLayer policy for vapi_update_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 vapi_update_assistant? +

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