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x402engine Claude Sonnet (claude-sonnet) LLM API
x402
x402engine Claude Sonnet (claude-sonnet) LLM API is a paid API for AI agents from x402engine.app, paid per call via x402, $0.083743/call, status unknown (last checked 2026-10-12).
Send OpenAI-compatible chat messages to Claude Sonnet and receive AI-generated text responses, paid per call via USDC micropayment.
Price / call$0.083743
Success—
StatusUnknown
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 response with a choices array containing the assistant message (role: assistant, content: generated text), finish_reason (e.g. 'stop'), and the model name. Also returns a top-level 'content' shortcut field with the raw text. If streaming is enabled, returns Server-Sent Events (SSE) in OpenAI format.
Example use cases
AI agent reasoning step
“Send this user's question to Claude Sonnet and return its answer: 'What are the top five risks of deploying LLMs in production?' I want streaming enabled so I can display the response as it comes in.”
Function-calling workflow automation
“Use Claude Sonnet to process this support ticket and call the 'categorize_ticket' function I've defined — the function takes a category string and urgency level. Here's the ticket: 'My payment failed three times and I can't reach support.'”
Document analysis with file input
“Have Claude Sonnet read this PDF I'm uploading and summarize its key findings in bullet points — use the native PDF parser and keep the summary under 200 words.”
Technical details
Endpoint
POSThttps://x402engine.app/api/llm/claude-sonnet?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need Claude Sonnet's strong reasoning, instruction-following, and multimodal (text + image + PDF) capabilities on a pure pay-per-call basis without an Anthropic API subscription or monthly commitment. Ideal for AI agents that make sporadic or bursty calls to a frontier model, want OpenAI-compatible message formats with tool/function calling, or need to pay in USDC on Base/Solana or USDm on MegaETH. Prefer over raw Anthropic API when you want zero-setup micropayment billing.
Side effects
- Payment not settled — 402 returned if USDC/USDm payment is not included or insufficient
- Invalid messages format — missing required 'messages' array or malformed role values
- Unsupported parameters — top_k or other model-specific params not supported by Claude Sonnet
- Context length exceeded — messages array too long for model's context window
- Tool call schema error — malformed function definition causes rejection
- Stream not supported — some configurations may not support SSE streaming
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"model": "anthropic/claude-sonnet-4.5",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "Hello!"
},
"finish_reason": "stop"
}
],
"content": "Hello!"
}
}Tags
x402
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