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x402 LLM Gateway
x402
x402 LLM Gateway is a paid API for AI agents from x402.alexk.is, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-18).
OpenAI-compatible chat completions endpoint that charges $0.01 USDC per call via the x402 on-chain micropayment protocol on Base.
Price / call$0.01
Success—
StatusUnknown
How this service works
OpenAI-compatible chat completions, priced per call at $0.01 USDC on Base. Payment uses the x402 protocol: an unpaid request returns HTTP 402 with a PAYMENT-REQUIRED header; the client signs a USDC transfer, retries with a PAYMENT-SIGNATURE header, and the facilitator settles on-chain.
Output
Returns an OpenAI-format chat completion object containing: a unique completion ID, the model used, a choices array with the assistant's message content, role, and finish reason, plus a Unix timestamp of when the response was created.
Example use cases
Per-call AI for autonomous agents
“I'm building an agent that needs to call an LLM occasionally without a monthly subscription — can you send this conversation to the x402 LLM gateway and pay the per-call USDC fee? Messages: [{"role":"user","content":"Summarize the key risks in this contract clause: indemnification applies to gross negligence."}]”
Crypto-native chatbot prototype
“Use the x402 chat completions endpoint to reply to my user's message: 'What are the top three DeFi protocols on Base right now?' — keep the response concise, max 200 tokens, and settle the micropayment on-chain.”
Low-volume research assistant
“Send this question to the pay-per-use LLM gateway: 'Give me a step-by-step outline for a literature review on transformer attention mechanisms' — temperature 0.7, and go ahead and handle the USDC payment automatically.”
Technical details
Endpoint
GEThttps://x402.alexk.is/v1/chat/completions?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need OpenAI-compatible chat completions with true pay-per-call billing in USDC on Base — ideal for autonomous agents, low-volume workloads, or crypto-native apps that want no subscription commitment and on-chain auditability of each inference cost. Prefer it over standard OpenAI or Anthropic APIs when your agent already handles x402 payment flows or when you need stablecoin-denominated AI spend.
Side effects
- HTTP 402 returned if no payment signature is included — client must sign a USDC transfer and retry with PAYMENT-SIGNATURE header
- Payment signature invalid or USDC balance insufficient — transaction rejected by facilitator
- Model ID not found — returns error if unsupported model is specified
- Malformed messages array — missing required 'role' or 'content' fields causes 400 error
- Rate limit or upstream LLM unavailability — gateway may return 503 or timeout
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| model | string | Model id. Omit to use the default. |
| messagesrequired | array | Conversation so far, oldest first. |
| max_tokens | integer | |
| temperature | number |
Output
Schema · Response
| Field | Type | Description |
|---|---|---|
| id | string | |
| model | string | |
| object | string | |
| choices | array | |
| created | integer |
Tags
x402
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