# OpenAI GPT-5 Nano Chat Completions (x402/USDC)

> OpenAI GPT-5 Nano 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 Nano chat completions via a pay-per-call x402 API billed in USDC, with selectable quality levels and service tiers.

## Facts

- Endpoint: POST https://openai.mm.family/x402/v1/models/gpt-5-nano/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-nano-chat-completions-x402-usdc-87a378f8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_1uBmjvhrRCn-5t5ne6z-s

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-nano-chat-completions-x402-usdc-87a378f8 -d '<json body>'
```

Example prompt: Send this message to GPT-5 Nano at the 'high' quality level using the standard service tier: 'Explain the difference between supervised and unsupervised learning in three sentences.' Give me up to 300 tokens in the response.

## When to prefer this

Choose this endpoint when you need the cheapest OpenAI-compatible chat completions with per-call USDC billing — ideal for high-volume, cost-sensitive pipelines, crypto-native apps that avoid traditional API keys, or scenarios where you want to tune quality vs cost via model level (minimal/low/medium/high) and service tier (flex vs standard). Prefer it over gpt-4o or gpt-5.4-mini siblings when token cost is the primary constraint.

## Known failure modes

- Insufficient USDC payment causes 402 Payment Required response
- Invalid model enum value returns 400 Bad Request
- max_tokens quota exceeded leads to truncated response with finish_reason='length'
- Invalid service_tier value returns validation error
- Network or upstream OpenAI outage causes 502/503 errors
- Malformed messages array (missing role or content) causes 400 error

## How this service works

gpt-5-nano: OpenAI GPT 5 Nano chat completions, paid per call in USDC. Per 1M tokens in/out: Flex (default) 0.025/0.2, Standard 0.05/0.4; pick with service_tier. Plus $0.0005 (Base) or $0.0005 (Solana) per call; the quote charges input plus 10% of max_tokens. Levels: minimal, low, medium, high (model gpt-5-nano:<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, finish reason (e.g. 'stop'), prompt and completion token counts, the model variant used, and the service tier applied. Empty responses when the answer is empty are billed at zero.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "enum": [
    "gpt-5-nano",
    "gpt-5-nano:minimal",
    "gpt-5-nano:low",
    "gpt-5-nano:medium",
    "gpt-5-nano: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-nano",
  "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-nano-chat-completions-x402-usdc-87a378f8/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)