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x402engine GPT-5 Nano LLM API
x402
x402engine GPT-5 Nano LLM API is a paid API for AI agents from x402engine.app, paid per call via x402, $0.001773/call, status unknown (last checked 2026-10-12).
Runs OpenAI GPT-5 Nano chat completions via pay-per-call HTTP 402 micropayment, returning an OpenAI-compatible response
Price / call$0.001773
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 object with a choices array containing the assistant message, finish_reason ('stop', 'tool_calls', etc.), and model name ('openai/gpt-5-nano'). Optionally streams SSE tokens if stream=true.
Example use cases
Agent reasoning with cheap LLM
“Use GPT-5 Nano to decide which of these three options is best for my user — system prompt: 'You are a decision assistant', user message: 'Should I invest in stocks, bonds, or real estate given a 5-year horizon and moderate risk tolerance?' Pay per call.”
Tool-calling pipeline step
“Call GPT-5 Nano with my messages array and these two function definitions — get_weather and search_web — so it can decide which tool to invoke next in my agent workflow.”
Streaming chat response
“Send my chat history to GPT-5 Nano with streaming enabled so I get tokens back in real time: system is 'You are a coding tutor', user says 'Explain Python decorators with a short example.'”
Technical details
Endpoint
POSThttps://x402engine.app/api/llm/gpt-5-nano?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a cheap, fast OpenAI-compatible chat completion (GPT-5 Nano) and want to pay per call in USDC on Base without an OpenAI subscription. Ideal for AI agent pipelines that need cost-controlled LLM inference with tool calling and streaming support, especially when the agent already handles x402 micropayment headers.
Side effects
- 402 Payment Required if USDC balance is insufficient or payment settlement fails
- 400 Bad Request if messages array is missing or malformed
- Model-level refusal if content policy is triggered (finish_reason=content_filter)
- Timeout or partial stream if network drops mid-SSE stream
- Invalid tool definition schema causes tool_calls to fail silently
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"model": "openai/gpt-5-nano",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "Hello!"
},
"finish_reason": "stop"
}
],
"content": "Hello!"
}
}Tags
x402
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