# GPT-5.5 Metered Chat Completions (GET, x402 Guarantee Deposit)

> GPT-5.5 Metered Chat Completions (GET, x402 Guarantee Deposit) is a paid API for AI agents from gpt55.558686.xyz, paid per call via x402, $0.523889/call, status unknown (last checked 2026-09-15).

GET-based OpenAI-compatible GPT-5.5 chat completions endpoint with usage-metered x402 pricing and a pre-payment guarantee deposit quote of $0.523889 USDC; unused deposit is credited back after actual usage is settled.

## Facts

- Endpoint: GET https://gpt55.558686.xyz/v1/chat/completions/metered
- Price: $0.523889/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gpt-5-5-metered-chat-completions-get-x402-guarantee-deposit-c1f6ff6e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_J9OsG0-Ci5Qqbkiy2b2vY

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-5-5-metered-chat-completions-get-x402-guarantee-deposit-c1f6ff6e
```

Example prompt: Ask GPT-5.5 the following using metered x402 pricing — system prompt: 'You are a helpful assistant', message: 'Explain quantum entanglement in simple terms', max 500 tokens, and give me the $0.523889 guarantee deposit quote before we proceed.

## When to prefer this

Choose this endpoint when you need GPT-5.5 chat completions via a GET request (useful for browser, curl, or agent environments that cannot easily POST JSON bodies), want usage-metered x402 micropayment billing with a transparent pre-payment deposit, and prefer discounted token rates (input $5/1M, cached $0.5/1M, output $30/1M multiplied by 0.111112) with automatic credit-back of unused deposit. Prefer over POST variants when query-parameter-based invocation is required.

## Known failure modes

- Payment not provided or x402 payment header missing — returns 402 Payment Required
- Model parameter not set to 'gpt-5.5' — may return 400 Bad Request or route mismatch
- max_tokens exceeds 128000 — schema validation error
- No prompt/input/message query parameter provided — returns 400 missing required input
- Upstream OpenAI API unavailable — 502 or 503 proxy error
- Deposit insufficient for actual usage — may result in balance adjustment or partial response

## 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-compatible chat completion object with an id, object type, model name, choices array containing the assistant's message, and a usage object detailing prompt/completion token counts. The $0.523889 USDC guarantee deposit is charged upfront; any unused portion is credited back to the caller's internal balance once upstream token usage is confirmed.

## 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-luna",
        "gpt-5.6-terra",
        "gpt-5.5",
        "gpt-5.3-codex",
        "gpt-5.4"
       ],
       "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-5.5."
    },
    "finish_reason": "stop"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gpt-5-5-metered-chat-completions-get-x402-guarantee-deposit-c1f6ff6e/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)