# Model Access Gateway – GPT-6 Luna Chat Completions (x402, USDC)

> Model Access Gateway – GPT-6 Luna Chat Completions (x402, USDC) is a paid API for AI agents from modelaccessgateway.com, paid per call via x402, $0.0014/call, status unknown (last checked 2026-10-16).

Runs OpenAI-compatible chat completions against the gpt-6-luna model, paid per call in USDC via x402 with no account or API key required.

## Facts

- Endpoint: POST https://modelaccessgateway.com/llm/gpt-6-luna?utm_source=zero.xyz
- Price: $0.0014/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/model-access-gateway-gpt-6-luna-chat-completions-x402-usdc-cfa9e717
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_MnErCtUL6tFP4LnVvdGuP

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 model-access-gateway-gpt-6-luna-chat-completions-x402-usdc-cfa9e717 -d '<json body>'
```

Example prompt: Using the pay-per-call LLM gateway (no API key needed, billed in USDC), send this conversation to GPT-6 Luna: system prompt 'You are a helpful assistant', user message 'Explain quantum entanglement in two sentences', max 300 tokens, temperature 0.7.

## When to prefer this

Choose this endpoint when you need OpenAI-compatible chat completions without an API key or subscription, want to pay micropayments per call in USDC on Base using the x402 protocol, need an automatic refund guarantee if the model fails, or are building an autonomous agent that must self-fund LLM calls via crypto wallet. Prefer it over direct OpenAI or other providers when account-free, pay-per-use stablecoin billing is a hard requirement.

## Known failure modes

- Payment rejected or insufficient USDC balance — x402 payment handshake fails before inference runs
- Model unavailable or upstream provider error — endpoint returns an error but triggers automatic refund
- Invalid messages array (empty or missing required role field) — 400 validation error
- max_tokens exceeds 16384 — schema validation error
- Temperature outside 0–2 range — validation error
- Network timeout on long completions — especially relevant for streaming responses
- Malformed response_format object — may cause model to ignore formatting instructions

## How this service works

LLM inference API: OpenAI-compatible chat completions for 136 AI models (Claude, GPT, Gemini, Grok, DeepSeek, Qwen, Kimi, GLM), paid per call in USDC on Base with x402. No account, no API key, automatic refund if the model fails.

## Output

Returns a standard OpenAI-format chat.completion JSON object containing the assistant's reply message, finish reason (e.g. 'stop'), prompt/completion/total token counts, model name, and a unique completion ID. Supports streaming via server-sent events when stream=true. Automatic refund is issued if the model call fails.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "type": "string",
   "description": "Optional: fixed by the route (openai/gpt-6-luna)"
  },
  "tools": {
   "type": "array"
  },
  "stream": {
   "type": "boolean",
   "description": "true: server-sent events after payment"
  },
  "messages": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "role"
    ],
    "properties": {
     "role": {
      "enum": [
       "system",
       "user",
       "assistant",
       "tool",
       "developer"
      ],
      "type": "string"
     },
     "content": {
      "type": [
       "string",
       "array",
       "null"
      ]
     }
    }
   },
   "minItems": 1
  },
  "max_tokens": {
   "type": "integer",
   "maximum": 16384,
   "minimum": 1,
   "description": "Optional, default 4096"
  },
  "temperature": {
   "type": "number",
   "maximum": 2,
   "minimum": 0
  },
  "response_format": {
   "type": "object"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": "chatcmpl-7f3c2a91",
  "model": "openai/gpt-6-luna",
  "usage": {
   "total_tokens": 10,
   "prompt_tokens": 9,
   "completion_tokens": 1
  },
  "object": "chat.completion",
  "choices": [
   {
    "index": 0,
    "message": {
     "role": "assistant",
     "content": "OK"
    },
    "finish_reason": "stop"
   }
  ],
  "created": 1791979200
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/model-access-gateway-gpt-6-luna-chat-completions-x402-usdc-cfa9e717/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from modelaccessgateway.com](https://www.zero.xyz/host/modelaccessgateway.com/llms.txt)