# OpenAI GPT-4o Chat Completions (x402/USDC)

> OpenAI GPT-4o Chat Completions (x402/USDC) is a paid API for AI agents from openai.mm.family, paid per call via x402, $0.001027/call, status unknown (last checked 2026-10-02).

Runs GPT-4o chat completions via a pay-per-call USDC micropayment gateway, billed on token usage with Standard or Fast service tiers.

## Facts

- Endpoint: POST https://openai.mm.family/x402/v1/models/gpt-4o/chat/completions?utm_source=zero.xyz
- Price: $0.001027/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-4o-chat-completions-x402-usdc-5d604be1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vVfwrzirFchIIgoa8QIzu

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-4o-chat-completions-x402-usdc-5d604be1 -d '<json body>'
```

Example prompt: Using GPT-4o with the Standard service tier, answer this question with a maximum of 500 tokens: 'What are the key differences between supervised and unsupervised machine learning?'

## When to prefer this

Choose this endpoint when you need GPT-4o quality chat completions without an OpenAI subscription, want to pay per call in USDC via the x402 protocol, or are building a crypto-native or agentic workflow that requires pay-as-you-go LLM access. Prefer the Standard tier for cost efficiency and Fast tier when latency is critical. Use this over raw OpenAI API when you lack API keys or want programmatic USDC billing.

## Known failure modes

- Insufficient USDC balance or failed x402 payment — request rejected before processing
- max_tokens set too low — response truncated with finish_reason 'length'
- Invalid or missing messages array — 400 Bad Request
- Rate limits or quota exceeded on the upstream OpenAI API — 429 or 503
- Streaming not supported in all client configurations — may require specific handling
- Empty or trivial prompts return empty answers at no charge but yield no useful content

## How this service works

gpt-4o: OpenAI GPT 4o chat completions, paid per call in USDC. Per 1M tokens in/out: Standard (default) 2.5/10.0, Fast 4.25/17.0; pick with service_tier. Plus $0.0005 (Base) or $0.0005 (Solana) per call; the quote charges input plus 10% of max_tokens. Empty answers are free. Rates: https://openai.mm.family/x402/pricing

## Output

Returns a standard OpenAI chat completion JSON object containing the assistant's reply message, role, finish_reason (e.g. 'stop'), token usage breakdown (prompt, completion, total), the model name, and the service_tier used. Choices array contains one or more candidate responses.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "enum": [
    "gpt-4o"
   ],
   "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-4o",
  "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": "default"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/openai-gpt-4o-chat-completions-x402-usdc-5d604be1/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)