# Model Access Gateway – Claude Sonnet 5.5 (x402 Pay-Per-Call)

> Model Access Gateway – Claude Sonnet 5.5 (x402 Pay-Per-Call) 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 an OpenAI-compatible chat completion request against Claude Sonnet 5.5 (Anthropic), paid per call in USDC on Base via x402, with no API key or account required.

## Facts

- Endpoint: POST https://modelaccessgateway.com/llm/claude-sonnet-5.5?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-claude-sonnet-5-5-x402-pay-per-call-0b849caf
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_B501JybB0IQ2hCngZkI1I

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-claude-sonnet-5-5-x402-pay-per-call-0b849caf -d '<json body>'
```

Example prompt: Ask Claude Sonnet 5.5 to summarize the following meeting transcript in three bullet points, paying with USDC on Base — no API key needed: [transcript text]

## When to prefer this

Prefer this endpoint when you need Claude Sonnet 5.5 specifically (Anthropic's model) without managing an Anthropic account or API key, want true pay-per-call billing in USDC (no monthly subscription), are building autonomous agents that need self-sovereign access to frontier models, or need OpenAI-compatible request format with automatic crypto micropayment handling via x402.

## Known failure modes

- Insufficient USDC balance — payment rejected before inference runs
- Model failure — automatic refund issued, no charge
- Invalid messages array (empty or malformed) — 400 error
- max_tokens out of range (must be 1–16384) — 400 validation error
- temperature out of range (0–2) — 400 validation error
- Streaming not supported by client — SSE parsing errors if stream:true
- Network timeout before response completes — partial or no output

## 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, token usage (prompt, completion, total), finish reason (e.g. 'stop'), model identifier ('anthropic/claude-sonnet-5.5'), and a unique completion ID. Streaming mode delivers server-sent events. Payment is deducted per call in USDC; automatic refund is issued if the model fails.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "type": "string",
   "description": "Optional: fixed by the route (anthropic/claude-sonnet-5.5)"
  },
  "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": "anthropic/claude-sonnet-5.5",
  "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-claude-sonnet-5-5-x402-pay-per-call-0b849caf/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)