# OpenAI GPT-5.1 Chat Completions (x402/USDC)

> OpenAI GPT-5.1 Chat Completions (x402/USDC) is a paid API for AI agents from openai.mm.family, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-02).

Runs OpenAI GPT-5.1 chat completions via a pay-per-call USDC gateway, with selectable service tiers (Flex, Standard, Fast) and reasoning levels

## Facts

- Endpoint: POST https://openai.mm.family/x402/v1/models/gpt-5.1/chat/completions?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/openai-gpt-5-1-chat-completions-x402-usdc-05587275
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_swsmw0JBwtX5j1DB5jvJV

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 openai-gpt-5-1-chat-completions-x402-usdc-05587275 -d '<json body>'
```

Example prompt: Using GPT-5.1 on standard tier with high reasoning, answer this multi-step logic problem for me: 'A farmer has 17 sheep, all but 9 die — how many are left?' and limit the response to 200 tokens.

## When to prefer this

Choose this endpoint when you need GPT-5.1 specifically (vs GPT-5-nano or GPT-5.2) and want pay-per-call USDC billing without an OpenAI subscription. Prefer the Flex tier for cost-sensitive batch workloads, Standard for balanced throughput, and Fast for latency-critical agent loops. Use the reasoning level suffix (none/low/medium/high) when you need to control compute depth for complex tasks.

## Known failure modes

- Insufficient USDC balance — payment fails before inference runs
- max_tokens too low — model truncates output at limit with finish_reason='length'
- Invalid model enum value — 400 error if model string not in allowed list
- Rate limit exceeded on chosen service tier — 429 response
- Malformed messages array (missing role or content) — 422 validation error
- Network timeout on fast/flex tier during high load

## How this service works

gpt-5.1: OpenAI GPT 5.1 chat completions, paid per call in USDC. Per 1M tokens in/out: Flex (default) 0.625/5.0, Standard 1.25/10.0, Fast 2.5/20.0; pick with service_tier. Plus $0.0005 (Base) or $0.0005 (Solana) per call; the quote charges input plus 10% of max_tokens. Levels: none, low, medium, high (model gpt-5.1:<level>). Empty answers are free. Rates: https://openai.mm.family/x402/pricing

## Output

Returns a JSON chat completion object containing the assistant's reply message, token usage breakdown (prompt, completion, total), finish reason, model name, service tier used, and a unique completion ID. Empty completions (e.g. for quota checks) are returned free of charge.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "enum": [
    "gpt-5.1",
    "gpt-5.1:none",
    "gpt-5.1:low",
    "gpt-5.1:medium",
    "gpt-5.1:high"
   ],
   "type": "string"
  },
  "tools": {
   "type": "array"
  },
  "stream": {
   "type": "boolean"
  },
  "messages": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "role",
     "content"
    ],
    "properties": {
     "role": {
      "type": "string"
     },
     "content": {
      "type": "string"
     }
    }
   }
  },
  "max_tokens": {
   "type": "integer"
  },
  "service_tier": {
   "enum": [
    "flex",
    "default",
    "standard",
    "auto",
    "fast",
    "priority"
   ],
   "type": "string"
  },
  "response_format": {
   "type": "object"
  },
  "reasoning_effort": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": "chatcmpl-x",
  "model": "gpt-5.1",
  "usage": {
   "total_tokens": 9,
   "prompt_tokens": 8,
   "completion_tokens": 1
  },
  "object": "chat.completion",
  "choices": [
   {
    "index": 0,
    "message": {
     "role": "assistant",
     "content": "Hello",
     "refusal": null
    },
    "finish_reason": "stop"
   }
  ],
  "service_tier": "flex"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/openai-gpt-5-1-chat-completions-x402-usdc-05587275/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from openai.mm.family](https://www.zero.xyz/host/openai.mm.family/llms.txt)