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GPT Mini API (Pay-per-call Chat Completions)
x402
GPT Mini API (Pay-per-call Chat Completions) is a paid API for AI agents from x402.agentindex.world, paid per call via x402, $0.005069/call, status unknown (last checked 2026-10-01).
Pay-per-call OpenAI-format chat completions using GPT-4o-mini via OpenRouter, with no API key required — billed per request via x402 micropayment.
Price / call$0.005069
Success—
StatusUnknown
How this service works
GPT Mini API - pay per call, no API key. OpenAI-format chat completions on openai/gpt-5.4-mini, pinned to OpenAI's own OpenRouter endpoint for reliability. You sign a fixed price computed from your max_tokens; unused tokens are not refunded. 20s server-side timeout - never charged if it fires; set your client timeout to 30s. Try GET /llm/gpt-mini/sample.
Output
Returns an OpenAI-format chat completion object containing the assistant's generated reply text, finish reason, and token usage details. The response mirrors the standard OpenAI /v1/chat/completions response shape.
Example use cases
Quick LLM answer without API key
“I need a one-off GPT response to this question: 'Explain the difference between REST and GraphQL in two sentences.' Use up to 150 tokens and bill me per call — I don't want to set up an OpenAI account.”
Automated chatbot reply generation
“My support bot needs a reply to a customer message: 'Where is my order?' — generate a polite holding response using GPT, max 100 tokens, and charge me per call.”
Dynamic content generation in a pipeline
“In my data pipeline, generate a one-paragraph product description for 'wireless noise-cancelling headphones for remote workers' — keep it under 200 tokens and use the pay-per-call GPT endpoint so I'm not locked into a monthly plan.”
Technical details
Endpoint
GEThttps://x402.agentindex.world/llm/gpt-mini?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a quick, keyless GPT-4o-mini chat completion without setting up an OpenAI account or managing API credentials. Ideal for agents that make infrequent or unpredictable LLM calls and want transparent per-call USDC pricing with a known cost ceiling set by max_tokens. Not suitable for streaming responses, long context windows beyond 4096 tokens, or high-volume workloads where a direct OpenAI subscription would be cheaper.
Side effects
- 20-second server-side timeout fires — request is never charged but the client receives no completion
- max_tokens exceeds 4096 cap — request may be rejected or clamped
- Malformed messages array (missing role or content) — likely a 4xx validation error
- Payment failure or insufficient USDC balance — x402 payment rejected before processing
- Network timeout on client side if client timeout is set below 30s — client should use 30s minimum
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| messages | array | OpenAI-format chat messages: [{role, content}, ...]. |
| max_tokens | integer | Max completion tokens, capped at 4096 - also bounds the price ceiling. |
Tags
x402
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