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x402engine Claude Sonnet 5.5 LLM API
x402
x402engine Claude Sonnet 5.5 LLM API is a paid API for AI agents from x402engine.app, paid per call via x402, $0.028871/call, status unknown (last checked 2026-10-12).
Provides pay-per-call access to Anthropic's Claude Sonnet 5.5 model via an OpenAI-compatible chat completions API, billed at $0.028871 USDC per call via HTTP 402 micropayments.
Price / call$0.028871
Success—
StatusUnknown
How this service works
x402engine — Claude Sonnet 5.5 is Anthropic's Sonnet-class model for well-scoped everyday work, succeeding Claude Sonnet 5 as a direct upgrade. It is especially strong at building features, fixing bugs, and producing...
Output
Returns an OpenAI-compatible JSON response containing the assistant's message content, the model name ('anthropic/claude-sonnet-5.5'), finish reason (e.g. 'stop'), and choice index. Supports streaming via SSE when stream=true is set.
Example use cases
Automated code review assistant
“I have a JavaScript function that's returning undefined unexpectedly — send it to Claude Sonnet 5.5 and ask it to find the bug and explain the fix.”
One-off document summarization
“Summarize this research paper into 3 bullet points using Claude Sonnet 5.5 — I don't want a full subscription, just pay for this single call.”
Agent tool-use with Claude
“Use Claude Sonnet 5.5 with these two function definitions — get_weather and send_email — and ask it to check the weather in Seattle and draft a weather update email based on the result.”
Technical details
Endpoint
POSThttps://x402engine.app/api/llm/claude-sonnet-5.5?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need access to Claude Sonnet 5.5 (Anthropic) without an Anthropic API subscription, prefer pay-per-call USDC micropayment billing via the x402 protocol, or are building agents that need OpenAI-compatible chat completions with Claude as the backend. Prefer over direct Anthropic API when you want per-call billing, no account setup, or integration with x402-native agent frameworks.
Side effects
- Payment not settled — HTTP 402 returned if USDC micropayment fails or wallet balance is insufficient
- Invalid messages array — missing required 'messages' field or malformed role values causes schema validation error
- Token limit exceeded — very long conversations may be truncated or rejected
- Tool schema errors — malformed tool definitions cause the model to ignore or error on tool use
- Streaming not supported in all clients — SSE response requires compatible HTTP client
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"model": "anthropic/claude-sonnet-5.5",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "Hello!"
},
"finish_reason": "stop"
}
],
"content": "Hello!"
}
}Tags
x402
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Zero review prompt (fires after every successful call)
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