# GPT-5.6 Luna x402 Chat Completions (GET variant)

> GPT-5.6 Luna x402 Chat Completions (GET variant) is a paid API for AI agents from gpt55.558686.xyz, paid per call via x402, $0.049998/call, status down (last checked 2026-10-13).

Generates OpenAI-compatible chat completions using the GPT-5.6-terra/luna model via a GET request, paid per-call with USDC over x402.

## Facts

- Endpoint: GET https://gpt55.558686.xyz/v1/chat/completions/gpt-5.6-terra?utm_source=zero.xyz
- Price: $0.049998/call
- Payment: x402
- Status: down
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gpt-5-6-luna-x402-chat-completions-get-variant-759a0e60
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Dv_qFGQrqxbx1JFM_Sona

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 gpt-5-6-luna-x402-chat-completions-get-variant-759a0e60
```

Example prompt: Ask GPT-5.6 Luna to explain quantum entanglement in two sentences, using the gpt-5.6-terra model with a max of 200 tokens, and pay for the call with USDC.

## When to prefer this

Choose this endpoint when you need a pay-per-call, subscription-free LLM completion using x402 USDC micropayments on Base, especially in agent pipelines or browser-wallet contexts where you want to avoid API key management. Prefer it over standard OpenAI direct access when per-request billing in crypto is required, or when you need OpenAI-compatible output format with the gpt-5.6-luna/terra model tier specifically.

## Known failure modes

- Payment not included or insufficient USDC — returns 402 Payment Required
- Invalid or unsupported model enum value — returns 400 Bad Request
- Missing required 'input' or 'prompt' query parameter — returns 400
- Upstream model provider unavailable — returns 502 or 503
- max_tokens exceeds 128000 limit — validation error
- Rate limit or quota exceeded — returns 429

## How this service works

GPT-5.6 Luna API Base USDC and OpenAI-compatible x402 chat: one request for $0.00293, paid by browser wallet or a quote-first agent fallback.

## Output

Returns an OpenAI-style JSON chat completion object containing a choices array with the assistant's message content, finish reason, model name, completion ID, and token usage stats (prompt, completion, total tokens).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object",
     "additionalProperties": true
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "q": {
       "type": "string"
      },
      "input": {
       "type": "string"
      },
      "model": {
       "enum": [
        "gpt-5.6-sol",
        "gpt-5.6",
        "gpt-5.6-terra",
        "gpt-5.5"
       ],
       "type": "string"
      },
      "prompt": {
       "type": "string"
      },
      "system": {
       "type": "string"
      },
      "message": {
       "type": "string"
      },
      "max_tokens": {
       "type": "integer",
       "maximum": 128000,
       "minimum": 1
      },
      "system_prompt": {
       "type": "string"
      },
      "max_output_tokens": {
       "type": "integer",
       "maximum": 128000,
       "minimum": 1
      }
     },
     "additionalProperties": true
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "required": [
      "id",
      "object",
      "model",
      "choices"
     ],
     "properties": {
      "id": {
       "type": "string"
      },
      "model": {
       "type": "string"
      },
      "usage": {
       "type": "object"
      },
      "object": {
       "type": "string"
      },
      "choices": {
       "type": "array"
      }
     },
     "additionalProperties": true
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": "chatcmpl_example",
  "model": "gpt-5.6-luna",
  "usage": {
   "total_tokens": 44,
   "prompt_tokens": 32,
   "completion_tokens": 12
  },
  "object": "chat.completion",
  "choices": [
   {
    "index": 0,
    "message": {
     "role": "assistant",
     "content": "A concise answer from GPT-5.6 Luna."
    },
    "finish_reason": "stop"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gpt-5-6-luna-x402-chat-completions-get-variant-759a0e60/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from gpt55.558686.xyz](https://www.zero.xyz/host/gpt55.558686.xyz/llms.txt)