# x402 Gateway – OpenAI o4-mini (Fast Reasoning)

> x402 Gateway – OpenAI o4-mini (Fast Reasoning) is a paid API for AI agents from x402-gateway-production.up.railway.app, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-15).

Runs OpenAI's o4-mini small reasoning model via the x402 payment gateway for fast chain-of-thought inference on math, coding, and analysis tasks

## Facts

- Endpoint: POST https://x402-gateway-production.up.railway.app/api/llm/o4-mini
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-gateway-production-up-railway-app-f2027a16
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_pwdhR-f170Tll6yLto1m7

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-gateway-production-up-railway-app-f2027a16 -d '<json body>'
```

Example prompt: Use the o4-mini reasoning model to solve this: given a list of integers [3, 1, 4, 1, 5, 9], write a Python function that returns all pairs summing to 10 and explain the time complexity.

## When to prefer this

Choose this endpoint when you need fast, affordable chain-of-thought reasoning — especially for math, coding, logic, or structured analysis — and don't need the full power of a larger frontier model. Ideal for agent pipelines where cost efficiency matters and the task benefits from step-by-step reasoning over raw fluency.

## Known failure modes

- Payment not included or insufficient (HTTP 402) — x402 micropayment required of $0.03 USDC per call
- Invalid or malformed prompt body returns 400 Bad Request
- Model overloaded or upstream OpenAI error returns 500 or 503
- Rate limiting if too many concurrent requests are made
- Empty or missing messages field causes request rejection

## How this service works

OpenAI's latest small reasoning model — fast chain-of-thought for math, coding, and analysis

## Output

A text completion from OpenAI's o4-mini model containing the model's chain-of-thought reasoning and final answer, covering the math, code, or analytical task submitted in the prompt.

## Example request

```json
{
 "model": "o4-mini",
 "messages": [
  {
   "role": "user",
   "content": "Given a list of integers [3, 1, 4, 1, 5, 9], write a Python function that returns all pairs summing to 10 and explain the time complexity."
  }
 ],
 "max_tokens": 1000
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-gateway-production-up-railway-app-f2027a16/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-gateway-production.up.railway.app](https://www.zero.xyz/host/x402-gateway-production.up.railway.app/llms.txt)