OpenAI GPT-5.1 Chat Completions (x402/USDC)

x402

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

Price / call$0.001

Seller volume →—

Success—

StatusUnknown

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.

Example use cases

Complex reasoning with high effort

“I need GPT-5.1 to work through a difficult legal clause analysis for me — use the high reasoning level and standard service tier, and keep the output under 500 tokens.”

Fast low-cost question answering

“Use GPT-5.1 on flex tier to quickly answer: what are the top 3 differences between REST and GraphQL? Keep it concise, max 150 tokens.”

Agentic tool-calling workflow

“Set up a GPT-5.1 chat completion on standard tier with my custom tools list — I want the model to decide whether to call my 'search_web' tool or answer directly based on the user's question about current stock prices.”

Technical details

Endpoint

POSThttps://openai.mm.family/x402/v1/models/gpt-5.1/chat/completions?utm_source=zero.xyz

When to prefer

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.

Side effects

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

Input

Schema · Request body

Field	Type	Description
model	string
tools	array
stream	boolean
messages	array
max_tokens	integer
service_tier	string
response_format	object
reasoning_effort	string

Output

Schema · Response

{
  "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"
  }
}

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