# OpenAI GPT-5 Mini Chat Completions (x402)

> OpenAI GPT-5 Mini Chat Completions (x402) is a paid API for AI agents from openai.mm.family, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-03).

Provides GPT-5 Mini chat completions via a pay-per-call x402 API, billed in USDC with tiered pricing by speed and quality level.

## Facts

- Endpoint: POST https://openai.mm.family/x402/v1/models/gpt-5-mini/chat/completions?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-03
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/openai-gpt-5-mini-chat-completions-x402-5e2b33b3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_oIgA2bctlHViPkEMk4soy

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-mini-chat-completions-x402-5e2b33b3 -d '<json body>'
```

Example prompt: Using the GPT-5 Mini model at standard tier, send this conversation — system: 'You are a helpful assistant', user: 'Summarize the water cycle in two sentences' — and give me up to 200 tokens in the response.

## When to prefer this

Choose this endpoint when you need a cost-efficient, OpenAI-compatible chat completion model that accepts pay-per-call USDC micropayments via x402 — ideal for agents or pipelines that want to avoid subscription lock-in, need fine-grained cost control per call, or must operate on-chain. Prefer over GPT-4o siblings when lower per-token cost matters more than maximum capability. Use the 'minimal' or 'low' quality levels for high-volume, low-stakes tasks; use 'standard' or 'fast' tiers for latency-sensitive applications.

## Known failure modes

- Payment failure if USDC balance is insufficient for quoted cost
- Invalid model name returns 400 with enum validation error
- Empty or malformed messages array causes a 400 error
- Exceeding context window for chosen model level returns an error
- Streaming not supported on all tiers — may return 422 if stream:true is unsupported
- Rate limiting on fast tier during high demand

## How this service works

gpt-5-mini: OpenAI GPT 5 Mini chat completions, paid per call in USDC. Per 1M tokens in/out: Flex (default) 0.125/1.0, Standard 0.25/2.0, Fast 0.45/3.6; 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-mini:<level>). Empty answers are free. Rates: https://openai.mm.family/x402/pricing

## Output

Returns an OpenAI-compatible chat completion JSON object containing the assistant's message content, finish reason (e.g. 'stop'), token usage breakdown (prompt, completion, total), the model name, and the service tier used for the request.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "enum": [
    "gpt-5-mini",
    "gpt-5-mini:minimal",
    "gpt-5-mini:low",
    "gpt-5-mini:medium",
    "gpt-5-mini: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-mini",
  "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-mini-chat-completions-x402-5e2b33b3/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)