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x402engine GPT-4o Mini LLM API
x402
x402engine GPT-4o Mini LLM API is a paid API for AI agents from x402engine.app, paid per call via x402, $0.002458/call, status unknown (last checked 2026-10-11).
Runs OpenAI GPT-4o Mini inference via pay-per-call HTTP 402 micropayment, returning OpenAI-compatible chat completions
Price / call$0.002458
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
An OpenAI-compatible JSON response containing the model name, an array of choices each with a role='assistant' message and finish_reason, and a top-level 'content' shortcut field. Supports streaming SSE if stream=true is set.
Example use cases
Agent reasoning with tool calling
“I need GPT-4o Mini to analyze this JSON object of user activity and call my 'flag_suspicious' function if it detects any anomalies — send the messages array and the function definition, and pay with USDC on Base.”
Cheap summarization pipeline
“Summarize this 500-word news article into three bullet points using GPT-4o Mini — I want it fast and cheap, paying per call rather than a monthly subscription.”
Multimodal image question answering
“Look at this image URL and tell me what objects are visible in the foreground — use GPT-4o Mini with the image_url content type and return the assistant's answer.”
Technical details
Endpoint
POSThttps://x402engine.app/api/llm/gpt-4o-mini?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need OpenAI GPT-4o Mini inference on a pay-per-call basis without managing an OpenAI API key or monthly subscription — ideal for AI agents that must pay autonomously using USDC on Base, USDm on MegaETH, or USDC on Solana. Prefer this over direct OpenAI access when your agent runtime supports HTTP 402 micropayments, when call volume is unpredictable, or when you want crypto-native billing. It is a drop-in OpenAI-compatible interface so migration is minimal.
Side effects
- Payment not settled — 402 returned if USDC balance is insufficient or payment header is missing
- Unsupported parameter — if a capability like logprobs or seed is not supported by gpt-4o-mini, the field is silently ignored or returns an error per docs
- Malformed messages array — missing required 'role' or neither 'content' nor 'tool_calls' causes a 400 validation error
- Rate limits — upstream OpenAI throttling may cause 429 or delayed responses
- Streaming failure — SSE stream may drop if network is unstable after payment settlement
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"model": "openai/gpt-4o-mini",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "Hello!"
},
"finish_reason": "stop"
}
],
"content": "Hello!"
}
}Tags
x402
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