## The Issue Vapi's MCP integration creates a non-existent wrapper function instead of exposing actual MCP server tools, causing "Unknown tool" errors in production calls. ## Expected vs Actual Behavior MCP Server defines:

python
@mcp.tool
def get_appointment_timeslots(zip_code: str, address: str, city: str): pass

@mcp.tool  
def create_appointment(correlation_id: str, first_name: str, ...): pass

Should expose:

get_appointment_timeslots

and

create_appointment

Vapi exposes:

book_appointments

(doesn't exist in MCP server) ## Production Failure AI attempted

book_appointments

3 times, all failed:

json
// Request
{"function": {"name": "book_appointments", "arguments": "{\"action\": \"get_appointment_timeslots\", ...}"}}

// Response  
{"result": "[{\"type\": \"text\", \"text\": \"Unknown tool: book_appointments\"}]"}

Customer couldn't book appointment due to this bug. ## Root Cause Vapi incorrectly parses MCP

tools/list

JSON-RPC responses. Instead of exposing individual tools per the MCP specification, it creates a wrapper that doesn't exist. Vapi's tool config shows the mismatch:

json
{
  "function": {"name": "book_appointments"},  // ❌ Fake wrapper
  "metadata": {
    "tools": [
      {"function": {"name": "ngrokfree-get_appointment_timeslots"}},  // ✅ Real tools
      {"function": {"name": "ngrokfree-create_appointment"}}
    ]
  }
}

## Comparison Claude Desktop (works correctly): -

front-desk-appointment:get_appointment_timeslots

✅ -

front-desk-appointment:create_appointment

✅ ## Impact on MCP's Purpose This bug defeats the entire point of MCP. The protocol exists to expose groups of related tools through a single server, but Vapi's implementation forces developers to create individual tools one-by-one instead of leveraging MCP's server-based tool discovery. This makes MCP integration pointless on Vapi.

Hey, Can you send me the latest call_id? Along with that, can you provide me the duration in the recording where you had this issue?

@southern_push2935 any updates on this? i'm facing the same issue

no update