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fastapi.online Chat Completion
x402
fastapi.online Chat Completion is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.0015/call, status down (last checked 2026-09-15).
Send a list of messages to a self-hosted LLM and receive a chat completion response, billed per call via crypto with no signup required.
Price / call$0.0015
Success—
StatusDown
How this service works
Self-hosted AI API gateway. Expensive endpoints require an x402 micropayment (USDC on Base) before executing.
Output
Returns a JSON object containing the assistant's reply message (with role and content fields), the model name used, and usage statistics including prompt token count and completion token count.
Example use cases
Anonymous LLM Q&A for research bot
“Ask the AI to explain the difference between supervised and unsupervised machine learning in plain English — I don't want to sign up for anything, just pay per call with crypto.”
Multi-turn customer support draft
“I have a conversation thread where the user complained about a late delivery. Send it to the chat API with a system prompt saying 'You are a polite customer support agent' and temperature 0.3, and get a draft reply.”
Automated content summarization pipeline
“For each article I feed in, send the text as a user message to the LLM with the instruction 'Summarize this in 3 bullet points' and return the AI's response — I'll pay per call with USDC.”
Technical details
Endpoint
POSThttps://api.fastapi.online/chatWhen to prefer
Choose this endpoint when you need pay-per-call LLM chat completions with no account or subscription required, accepting crypto (USDC) micro-payments. Ideal for agents that need anonymous or frictionless AI inference, or when you want to avoid monthly API key commitments. Less suitable if you need guaranteed uptime SLAs, specific well-known hosted model names (GPT-4, Claude), or extensive usage dashboards.
Side effects
- Payment not provided or insufficient USDC — HTTP 402 returned requiring payment
- Missing required 'messages' field — validation error returned
- Invalid model name — may return error or fall back to default model
- Temperature out of expected range — may cause unexpected behavior
- Network timeout if inference takes too long for large prompts
- Malformed messages array — schema validation error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"model": "llama3.1:8b",
"usage": {
"prompt_tokens": 9,
"completion_tokens": 8
},
"message": {
"role": "assistant",
"content": "Hi! How can I help?"
}
}
}Tags
x402
Reviews
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Zero review prompt (fires after every successful call)
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