x402 examples — pay-per-call APIs for AI agents
Working examples for calling x402-gated HTTP APIs: your agent pays USDC per request on Base — no signup, no API keys, no subscription.
All examples run against x402.shizu.me (77 live
endpoints, prices from $0.001/call): an OpenAI-compatible LLM gateway
(/v1/chat/completions, /v1/embeddings, /v1/models), web search, a code
sandbox, web scraping, live crypto/market data, verifiable randomness, and a
prepaid off-chain metering rail for high-frequency loops (100+ calls/min,
no per-call gas).
How x402 works
- Call any endpoint → the
HTTP 402response carries signed USDC payment requirements (price, asset, recipient). - Pay — your x402 client signs the payment locally and retries automatically.
- Served — settlement is on-chain; you are only charged when the call succeeds. Errors and 4xx never settle.
Fund a wallet with a few dollars of USDC on Base, export its private key, and every example here just works.
JavaScript
npm install x402-fetch viem
export X402_PRIVATE_KEY=0x... # wallet holding USDC on Base
node js/chat.mjs
Python
pip install x402 eth-account httpx
export X402_PRIVATE_KEY=0x...
python python/chat.py
Examples
| File | What it shows |
|---|---|
js/chat.mjs | OpenAI-compatible chat completion, paid per call |
js/search.mjs | Live web search without a search-API account |
python/chat.py | Chat completion via the Python x402 client |
python/embeddings.py | OpenAI-shape embeddings for RAG loops |
python/metered_loop.py | Prepay once, then 100+ calls/min off-chain |
Just looking?
Every route quotes its price on a free unpaid request:
curl -i https://x402.shizu.me/crypto # → 402 + payment requirements
curl https://x402.shizu.me/llms.txt # full catalog, agent-readable
Links
Live service: https://x402.shizu.me · OpenAPI: https://x402.shizu.me/openapi.json · MCP tools: https://x402.shizu.me/.well-known/mcp-tools · Contact: x402@opklaar.com
MIT licensed.