Moduck

xAI: Grok 4.1 Fast

xAI's fast agentic tool-calling model with a 2M context window; non-reasoning variant for low-latency responses

Model lab
xAI
Model family
grok
Modalitiestext, image → text
Context window2,000,000
Maximum output30,000
InputUSD 0.16 / 1M tokens
OutputUSD 0.4 / 1M tokens
Try now

Quickstart

Use your Moduck API Key, set the API base URL to https://api.moduck.ai/v1, and set the model parameter to xai/grok-4.1-fast.

import os
import requests

base_url = "https://api.moduck.ai/v1"
api_key = os.environ["MODUCK_API_KEY"]
model_id = "xai/grok-4.1-fast"

response = requests.post(
    f"{base_url}/chat/completions",
    headers={
        "Authorization": f"Bearer {api_key}",
        "Content-Type": "application/json",
    },
    json={
        "model": model_id,
        "messages": [{"role": "user", "content": "Hello!"}],
        "stream": False,
    },
    timeout=60,
)
response.raise_for_status()
print(response.json())

Use the familiar OpenAI-style chat request format to make model integration easier.

Grok 4.1 Fast API Pricing

TypePrice information
InputUSD 0.16 / 1M tokens
OutputUSD 0.4 / 1M tokens
Cached inputUSD 0.04 / 1M tokens

Benchmarks

Non-reasoning

Intelligence Index · v4.311.3
Coding Index—
Agentic Index—

Reasoning

Intelligence Index · v4.320.4
Coding Index—
Agentic Index—

Performance

Performance trends

Throughput88.0 tok/sCurrent
Time to first token1.4 sCurrent
End-to-end latency7.1 sCurrent
Throughput
Current88.0 tok/s
Window average89.9 tok/s
Time to first token
Current1.4 s
Window average1.4 s
End-to-end latency
Current7.1 s
Window average7.5 s
Tail latency (P99)
Current14.5 s
Window average16.4 s
Prompt cache hit rate
Current18.1%
Window average24.6%
Error rate
Current0.0%
Window average0.2%

Availability

Uptime100%At least one provider responded
Availability100%Requests actually served
Error rate0%Share of failed requests
Served requests, hour by hour
24 hours agoNow

Grok 4.1 Fast Compare models

ModelInput priceOutput priceContext windowCapabilities
Grok 4.1 FastThis pageUSD 0.16 / 1M tokensUSD 0.4 / 1M tokens2,000,000Text output · Tool calling
Grok 4.6USD 1.6 / 1M tokensUSD 4.8 / 1M tokens500,000Text output · Reasoning · Tool calling
Grok 4.5USD 1.6 / 1M tokensUSD 4.8 / 1M tokens500,000Text output · Reasoning · Tool calling
Grok 4.1 Fast (Reasoning)USD 0.16 / 1M tokens · Context ≤ 1000000 tokens · Maximum output 1000000 tokensUSD 0.4 / 1M tokens · Context ≤ 1000000 tokens · Maximum output 1000000 tokens2,000,000Text output · Reasoning · Tool calling
Grok 4.7USD 1.6 / 1M tokensUSD 4.8 / 1M tokens500,000Text output · Reasoning · Tool calling

Model specifications

Input
text, image
Output
text
Context window
2,000,000
Maximum output
30,000
Release date
2025-11-19
Attachments
Yes
Reasoning
No
Tool calling
Yes
Structured output
Yes
Temperature setting
Yes
Open weights
No

Frequently asked questions

What is Grok 4.1 Fast for?

xAI's fast agentic tool-calling model with a 2M context window; non-reasoning variant for low-latency responses

What inputs and outputs does Grok 4.1 Fast support?

Recorded inputs: text, images; outputs: text.

How is Grok 4.1 Fast priced?

The pricing table shows the current recorded Moduck price. For example: Input USD 0.16 / 1M tokens; Output USD 0.4 / 1M tokens. See the pricing table for all units, variants, and conditions.

What specifications are recorded for Grok 4.1 Fast?

Current model records list Context window 2,000,000 tokens; Maximum output 30,000 tokens.

What model parameter does the Quickstart use?

The example uses xai/grok-4.1-fast. This value comes from the page identifier and is not confirmed as a callable Moduck public ID.

Can I call this model through the Moduck API now?

This page has no verified Moduck API call for this model. A Quickstart example or reserved ID does not establish access; check the models available to your account.