vapi-mcp-server

vapi_create_assistant

Create a new Vapi assistant by specifying name, model, voice, transcriber, first message, and server URL to enable voice AI interactions.

Instructions

Create a new Vapi assistant

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "name": "<name>"
    },
    "name": "vapi_create_assistant"
  }
}

Input Schema

Name	Required	Description	Default
`name`	Yes
`model`	No
`voice`	No
`transcriber`	No
`firstMessage`	No
`serverUrl`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Jun 21, 2026

TDQS

C2.3/5.0

Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description must disclose behavioral traits. It only states it creates a new assistant, but does not mention side effects, resource constraints, or any destructive aspects. This is inadequate for a creation tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness2/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely short (4 words), but this conciseness comes at the expense of necessary detail. It fails to front-load essential information for correct tool invocation.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness1/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given 6 parameters (including nested objects), no output schema, and no annotations, the description is severely incomplete. It does not explain return values, success conditions, or configuration details, leaving agents with insufficient context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters1/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, and the description provides no explanation of the six parameters (name, model, voice, etc.). It adds no meaning beyond the schema field names, leaving agents unaware of how to use them correctly.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Create a new Vapi assistant', which identifies the verb and resource. It distinguishes from siblings like vapi_list_assistants (listing) and vapi_delete_assistant (deleting). However, it lacks specificity about what 'assistant' encompasses.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No usage guidance is provided. The description does not indicate when to use this tool versus alternatives such as vapi_update_assistant or vapi_create_call, nor does it mention prerequisites or when not to use it.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.