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x402engine o4-mini LLM API
x402
x402engine o4-mini LLM API is a paid API for AI agents from x402engine.app, paid per call via x402, $0.008978/call, status unknown (last checked 2026-10-12).
Call OpenAI's o4-mini reasoning model via pay-per-call HTTP 402 micropayment, returning an OpenAI-compatible chat completion response.
Price / call$0.008978
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 chat completion object with model name ('openai/o4-mini'), a choices array containing the assistant message (role, content, tool_calls if applicable), finish_reason, and a top-level content field with the assistant's reply text.
Example use cases
On-demand reasoning for agent pipeline
“I need you to pass this problem to o4-mini: 'A train leaves city A at 60mph and another leaves city B at 80mph toward each other, 300 miles apart — when do they meet?' Use a system message saying you are a math tutor and return the full answer.”
Function-calling with o4-mini
“Call o4-mini with these messages and this tool definition: the tool is called get_weather with parameters city (string) and unit (enum: celsius, fahrenheit). User message is 'What's the weather in Tokyo in Celsius?' — return whatever tool_calls o4-mini produces.”
Streaming chat completion for live UI
“Send o4-mini the conversation so far — system: 'You are a coding assistant', user: 'Write a Python function to reverse a linked list' — and stream the response back to me so I can display it in real time.”
Technical details
Endpoint
POSThttps://x402engine.app/api/llm/o4-mini?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need OpenAI's o4-mini reasoning model on a pay-per-call basis using USDC micropayments (Base, Solana, or MegaETH), with no subscription or API key required. Ideal for AI agents that need low-cost, high-reasoning inference billed per request, especially in workflows where you want OpenAI-compatible tool use, streaming SSE, or PDF parsing without committing to a monthly plan.
Side effects
- Payment not settled — 402 response if USDC micropayment fails or wallet balance is insufficient
- Invalid messages array — 400 error if required 'messages' field is missing or malformed
- Context window exceeded — error if total token count surpasses o4-mini's context limit
- Tool schema invalid — error if function definitions are malformed or missing required 'function' key
- Rate limiting — upstream model provider throttling causing timeout or 429 response
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"model": "openai/o4-mini",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "Hello!"
},
"finish_reason": "stop"
}
],
"content": "Hello!"
}
}Tags
x402
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