# Claude Sonnet 4.6 via x402engine (Pay-per-call)

> Claude Sonnet 4.6 via x402engine (Pay-per-call) is a paid API for AI agents from x402engine.app, paid per call via x402, $0.042592/call, status unknown (last checked 2026-10-12).

Calls Anthropic's Claude Sonnet 4.6 LLM via a pay-per-call HTTP 402 micropayment endpoint, returning an OpenAI-compatible chat completion response.

## Facts

- Endpoint: POST https://x402engine.app/api/llm/claude-sonnet-4.6?utm_source=zero.xyz
- Price: $0.042592/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/claude-sonnet-4-6-via-x402engine-pay-per-call-b3d93a29
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_62TSwiQHGXIVL6siZOrv1

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 claude-sonnet-4-6-via-x402engine-pay-per-call-b3d93a29 -d '<json body>'
```

Example prompt: Send these messages to Claude Sonnet 4.6 and get a response: system prompt is 'You are a helpful assistant', and the user asks 'Explain the concept of zero-knowledge proofs in simple terms' — stream the reply back to me.

## When to prefer this

Choose this endpoint when you need Claude Sonnet 4.6 specifically (not a generic LLM), want pay-per-call billing in USDC/crypto without a monthly Anthropic subscription, are building an AI agent that handles its own micropayments via HTTP 402, or need OpenAI-compatible response format from a Claude model. Prefer over Anthropic's direct API when you want crypto-native billing or don't want to manage API key subscriptions.

## Known failure modes

- Insufficient USDC/crypto balance causes 402 payment required failure
- Malformed messages array (missing required role or content/tool_calls) causes 400 validation error
- Exceeding model context length causes truncation or 400 error
- Unsupported parameters (top_k, top_p) if model capability not available per /docs/llm-capabilities.md
- Streaming requested but client does not handle SSE correctly leading to garbled output
- Network timeout on long generations

## How this service works

125 production APIs behind HTTP 402 micropayments. 87 LLMs, Kling V3 and Hailuo video generation, image generation, code execution, travel search, web scraping, TTS, and transaction simulation. Pay with USDC on Base, USDm on MegaETH, or USDC on Solana.

## Output

Returns an OpenAI-compatible JSON chat completion object containing the model name (anthropic/claude-sonnet-4.6), a choices array with the assistant message content and finish reason, and optionally tool call payloads if tools were invoked.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "bodyType",
    "body",
    "method"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "messages"
     ],
     "properties": {
      "stop": {
       "oneOf": [
        {
         "type": "string"
        },
        {
         "type": "array",
         "items": {
          "type": "string"
         },
         "maxItems": 4
        }
       ],
       "description": "Model-supported stop; see /docs/llm-capabilities.md."
      },
      "tools": {
       "type": "array",
       "items": {
        "type": "object",
        "required": [
         "function"
        ],
        "properties": {
         "type": {
          "enum": [
           "function"
          ],
          "type": "string"
         },
         "function": {
          "type": "object",
          "properties": {
           "name": {
            "type": "string"
           },
           "strict": {
            "type": "boolean"
           },
           "parameters": {
            "type": "object"
           },
           "description": {
            "type": "string"
           }
          }
         }
        }
       },
       "description": "Client-executed function definitions; return results using role=tool and tool_call_id."
      },
      "top_k": {
       "type": "integer",
       "description": "Model-supported top_k; see /docs/llm-capabilities.md."
      },
      "top_p": {
       "type": "number",
       "description": "Model-supported top_p; see /docs/llm-capabilities.md."
      },
      "stream": {
       "type": "boolean",
       "description": "Return live OpenAI-compatible SSE after payment settlement."
      },
      "plugins": {
       "type": "array",
       "items": {
        "type": "object",
        "required": [
         "pdf"
        ],
        "properties": {
         "id": {
          "enum": [
           "file-parser"
          ],
          "type": "string"
         },
         "pdf": {
          "type": "object",
          "properties": {
           "engine": {
            "enum": [
             "native"
            ],
            "type": "string"
           }
          }
         }
        }
       },
       "description": "Optional native PDF parser only; automatically enabled for file inputs."
      },
      "messages": {
       "type": "ar
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "model": "anthropic/claude-sonnet-4.6",
  "choices": [
   {
    "index": 0,
    "message": {
     "role": "assistant",
     "content": "Hello!"
    },
    "finish_reason": "stop"
   }
  ],
  "content": "Hello!"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/claude-sonnet-4-6-via-x402engine-pay-per-call-b3d93a29/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402engine.app](https://www.zero.xyz/host/x402engine.app/llms.txt)