The Grid | Vapi

The Grid is an inference marketplace that serves models from several labs behind one OpenAI-compatible API. Its instrument IDs describe capability tiers rather than specific lab models.

text-standard, code-prime, and agent-max each route to a current model for that tier. When The Grid replaces an underlying model, an assistant can keep using the same instrument ID.

The Grid exposes an OpenAI-compatible Chat Completions API, so you can connect it to Vapi as a custom LLM.

Before starting, create an account with The Grid and a Consumption API key.

Add your credential

Send the following body to POST https://api.vapi.ai/credential. Use your Vapi private API key in the Authorization: Bearer <VAPI_PRIVATE_KEY> header:

{
  "provider": "custom-llm",
  "apiKey": "<YOUR THE GRID API KEY>"
}

Save the credential id from the response. Add it to the assistant’s credentialIds to select that credential.

Create the assistant

Send this body to POST https://api.vapi.ai/assistant with the same Vapi private API key. Set model.url to The Grid’s base URL and model.model to an instrument ID:

{
  "name": "My Assistant",
  "credentialIds": ["<YOUR THE GRID CREDENTIAL ID>"],
  "model": {
    "provider": "custom-llm",
    "url": "https://api.thegrid.ai/v1",
    "model": "text-standard",
    "metadataSendMode": "off",
    "maxTokens": 600,
    "messages": [
      {
        "role": "system",
        "content": "You are a helpful voice assistant. Keep replies short."
      }
    ]
  }
}

Setting metadataSendMode to off keeps Vapi call metadata out of requests to The Grid.

Choose an instrument

GET https://api.thegrid.ai/v1/models lists available instrument IDs. Check instrument specifications and pricing for current details. Examples include:

Instrument	Use it for
`text-standard`	General conversation. The usual starting point.
`text-prime`, `text-max`	More demanding questions; compare current speed and price.
`agent-standard`, `agent-max`	Multi-step tool use.
`code-standard`, `code-prime`	Assistants that read or write code.

Set `maxTokens` for spoken replies

Vapi uses 250 for maxTokens when it is omitted and sends the value to The Grid as max_tokens. A low cap can cut off a response.

The 600 value in the example is a starting point. Test your chosen instrument with representative spoken turns and raise the limit if replies are truncated. Keep the system prompt explicit about brevity.

Tool calling

The Grid’s API supports OpenAI-style function calling. To configure Vapi tools, see the tool calling integration guide. Test a tool call with your chosen instrument before relying on it.

Verify the assistant

Start a test call and ask the assistant a short question. Confirm it speaks a complete answer. Check the call logs for custom LLM errors. If you attached a tool, request an action that uses it. Confirm the tool runs.