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

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

## Facts

- Endpoint: POST https://openai.mm.family/x402/v1/models/gpt-5/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-chat-completions-x402-usdc-70ef2325
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_gW2McHLGM24XLsuZjw9Z5

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-chat-completions-x402-usdc-70ef2325 -d '<json body>'
```

Example prompt: Ask GPT-5 using the standard service tier and high quality level: 'Explain the implications of quantum computing for cryptography' — keep the response under 500 tokens.

## When to prefer this

Choose this endpoint when you need GPT-5 specifically (not GPT-4o or GPT-5-nano) and want to pay per call in USDC via the x402 protocol without a traditional OpenAI API key subscription. Ideal for agents operating in crypto-native or trustless environments, or when you want fine-grained control over cost vs. quality via service_tier (flex/standard/fast) and model level (minimal/low/medium/high). Prefer over the gpt-5-nano sibling when task complexity warrants the full GPT-5 capability.

## Known failure modes

- Insufficient USDC balance causes x402 payment failure and request rejection
- Invalid model variant (not in enum) returns 400 error
- Exceeding context window for the chosen model level returns an error
- Streaming not supported in some configurations, returns error if requested incompatibly
- max_tokens quota over-estimate leads to higher quote charge than actual usage

## How this service works

gpt-5: OpenAI GPT 5 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: minimal, low, medium, high (model gpt-5:<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 (e.g. 'stop'), the model used, and the active service tier. Empty responses when no tokens are consumed are free of charge.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "enum": [
    "gpt-5",
    "gpt-5:minimal",
    "gpt-5:low",
    "gpt-5:medium",
    "gpt-5: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",
  "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-chat-completions-x402-usdc-70ef2325/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)