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

> Model Access Gateway – GPT-6 Astra Chat Completions (x402, USDC) is a paid API for AI agents from modelaccessgateway.com, paid per call via x402, $0.0019/call, status unknown (last checked 2026-10-16).

Runs OpenAI-compatible chat completions against GPT-6 Astra, billed per-call in USDC via x402 with no account or API key required.

## Facts

- Endpoint: POST https://modelaccessgateway.com/llm/gpt-6-astra?utm_source=zero.xyz
- Price: $0.0019/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-astra-chat-completions-x402-usdc-eec3c903
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_LgD7Au5-azSnnEiZSkQiU

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-astra-chat-completions-x402-usdc-eec3c903 -d '<json body>'
```

Example prompt: Ask GPT-6 Astra to write a concise executive summary of the following text, paying per-call in USDC — no API key needed: 'Our Q3 revenue grew 18% YoY driven by enterprise upsells and reduced churn.'

## When to prefer this

Choose this endpoint when you need GPT-6 Astra specifically and want truly frictionless, account-free access — no API key provisioning, no subscription, just pay $0.0023 USDC per call on Base. Ideal for autonomous AI agents that manage their own crypto wallets, one-off tasks where setting up an OpenAI account is overkill, or multi-agent systems that need to spin up LLM calls dynamically with automatic refunds on model failure.

## Known failure modes

- Model provider error triggers automatic USDC refund
- Insufficient USDC balance results in 402 payment required error
- Invalid messages array (missing role or empty array) causes 400 validation error
- max_tokens exceeds 16384 limit returns schema validation error
- Unsupported role value in messages causes rejection
- Network timeout during streaming may result in partial response

## 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 an OpenAI-compatible chat.completion JSON object containing the assistant's message content, finish reason, token usage (prompt, completion, total), model identifier, and a unique completion ID. Streaming mode returns server-sent events with incremental content deltas.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "type": "string",
   "description": "Optional: fixed by the route (openai/gpt-6-astra)"
  },
  "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-astra",
  "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-astra-chat-completions-x402-usdc-eec3c903/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)