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x402engine GPT-5.4 LLM API
x402
x402engine GPT-5.4 LLM API is a paid API for AI agents from x402engine.app, paid per call via x402, $0.035747/call, status unknown (last checked 2026-10-20).
Calls OpenAI GPT-5.4 via HTTP 402 micropayment, returning an OpenAI-compatible chat completion response
Price / call$0.035747
Success—
StatusUnknown
How this service works
x402engine — OpenAI's unified flagship model — 1M context, computer use, top-tier across all tasks
Output
Returns an OpenAI-compatible JSON chat completion object including the model name ('openai/gpt-5.4'), a choices array with the assistant message content, role, and finish_reason ('stop', 'tool_calls', etc.), plus a top-level 'content' field with the response text. Streaming mode returns OpenAI-compatible SSE events.
Example use cases
Agentic reasoning with tool calls
“I need you to send my conversation to GPT-5.4 with a tool definition for 'search_web' that takes a query string — the user asked 'What are the latest AI news headlines?' — and stream back whatever GPT-5.4 decides to do.”
Code generation on demand
“Ask GPT-5.4 to write a TypeScript function that validates an email address using a regex, using this system prompt: 'You are an expert TypeScript developer. Return only code, no explanation.'”
Multi-turn customer support draft
“I have a multi-turn conversation to complete: the system says 'You are a polite customer support agent for a SaaS product', the user said 'I can't log into my account', and the assistant previously said 'I can help with that. Can you share your email?' — now the user says 'Sure, it's john@example.com'. Send this to GPT-5.4 and get the next reply.”
Technical details
Endpoint
POSThttps://x402engine.app/api/llm/gpt-5.4?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need GPT-5.4 specifically (the latest OpenAI flagship model) on a pay-per-call basis without a monthly OpenAI subscription, especially in agentic pipelines that pay with USDC on Base, USDm on MegaETH, or USDC on Solana. Prefer it over other x402engine LLMs when you need OpenAI's most capable reasoning, tool use, and instruction-following. It is well-suited for agents that make infrequent or variable-volume calls and want to avoid subscription overhead.
Side effects
- Payment not settled — 402 response if USDC/USDm balance is insufficient
- Invalid messages array — missing required 'role' or 'content'/'tool_calls' field causes schema validation error
- Tool call schema malformed — function definition missing 'function' key
- Unsupported seed value — model may not honor seed if capability is not listed in /docs/llm-capabilities.md
- Rate limit or upstream OpenAI outage — proxied 5xx errors from underlying provider
- Stream requested but SSE not handled — client must support chunked transfer encoding
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"model": "openai/gpt-5.4",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "Hello!"
},
"finish_reason": "stop"
}
],
"content": "Hello!"
}
}Tags
x402
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