Name: Grok 4.20 Reasoning API
Brand: xAI

Overview

What is Grok 4.20 Reasoning API?

Grok 4.20 Reasoning — a large language model designed for advanced reasoning tasks. It excels at multi-step problem solving, logical analysis, and complex instruction following.

Technical Specifications
- Supported inputs: Image, Text
- Output: Text
- Context window: 2,000,000 tokens / Max output: 1,999,000 tokens
- Endpoint: /chat/completions

Performance Benchmarks
[embed]

Grok 4.20 Reasoning API Pricing
- Input: $2.6 / 1M tokens
- Output: $7.8 / 1M tokens

Where to Use Grok 4.20 Reasoning

Coding and code review
Generate, debug, and review code across languages, reading whole files or repos in a single prompt.

Agentic and multi-step workflows
Reliable tool-calling and instruction-following suit agent loops that plan, call tools, and iterate.

Long-document analysis
Summarize and extract from contracts, papers, and reports without aggressive chunking.

Code Sample
[embed]

Uptime and performance

Uptime (24h): 100%
Uptime (7d): 100%
Availability (24h): 100%
Error rate (24h): 0%

Measured on the AI/ML API gateway across live traffic. Figures are medians unless stated. Last updated 2026-10-12.

Use cases

Document understanding tasks: the model is documented as excelling at understanding documents, making it suited to reading, interpreting, and extracting meaning from text-heavy materials.

Long-horizon agentic tool calling: it is documented as strong for long-running agentic workflows, including extended tool use across multiple steps.

Coding and agents: one model listing explicitly describes it as best for “coding + agents,” indicating suitability for developer workflows that combine code generation with agent-style task execution.

Complex logic and math, scientific/technical analysis, and multi-step investigations: Oracle documents it as appropriate for higher-stakes reasoning work where accuracy matters, including these analytical use cases.

How to use Grok 4.20 Reasoning API

Install any OpenAI-compatible SDK, point it at api.aimlapi.com/v1, and set the model to x-ai/grok-4-20-0309-reasoning.

import requests

r = requests.post(
    "https://api.aimlapi.com/v1/chat/completions",
    headers={"Authorization": "Bearer " + AIMLAPI_KEY},
    json={
      "model": "x-ai/grok-4-20-0309-reasoning",
      "messages": [
        {
          "role": "user",
          "content": "Hello!"
        }
      ]
    },
)
print(r.json())

const r = await fetch("https://api.aimlapi.com/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "x-ai/grok-4-20-0309-reasoning",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ]
  }),
});
console.log(await r.json());

curl -X POST https://api.aimlapi.com/v1/chat/completions \
  -H "Authorization: Bearer $AIMLAPI_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"x-ai/grok-4-20-0309-reasoning","messages":[{"role":"user","content":"Hello!"}]}'

OpenAI-compatible — swap the base URL and it works with your existing SDK.