# Grok 4.1 Fast Reasoning

> xAI's most cost-effective reasoning model, featuring strong tool-calling capabilities and efficient knowledge base synthesis.

**ID**: `x-ai/grok-4.1-fast-reasoning`  
**Creator**: xAI  
**Category**: text  
**Context**: 131K tokens  
**Pricing**: BYOK — billed by your provider  
**Released**: 2026-05-31  
**Web page**: https://anyrouter.dev/model/x-ai/grok-4.1-fast-reasoning

**Input modalities**: text  
**Output modalities**: text  

**Tokenizer**: Grok

**Capabilities**: chat, streaming, function-calling

## Usage

**Endpoint**: `POST https://anyrouter.dev/api/v1/chat/completions`

```bash
curl https://anyrouter.dev/api/v1/chat/completions \
  -H "Authorization: Bearer $ANYROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "x-ai/grok-4.1-fast-reasoning",
  "messages": [
    {
      "role": "user",
      "content": "Say hi in 3 words."
    }
  ]
}'
```

## Providers

| Provider | Input | Output |
| --- | --- | --- |
| google-agent-platform-byok | BYOK — billed by your provider | — |

BYOK routes are billed by your own provider key — AnyRouter charges $0. Rates marked (list) are the provider's published list price.

## Source

- Upstream docs: https://docs.x.ai/docs/models