How I put a data product behind x402 so AI agents can buy it with USDC

A developer built Scout Packs, a B2B lead-pack data product gated behind Coinbase's x402 protocol so AI agents can pay per purchase in USDC on Base without accounts, API keys, or subscriptions. The implementation returns HTTP 402 responses with machine-readable payment terms, verifies on-chain settlement via an X-Payment header, and exposes a /.well-known/x402 manifest plus an MCP server with list_packs and buy_pack tools. Packs sell for $9 (25 leads), $15 (50 leads), and $25 (100 leads), delivered as JSON.

I sell verified B2B lead packs. For a one-off campaign, a $49/month data seat is a terrible deal — and for an AI agent, a subscription signup is a non-starter. Agents can't fill out billing forms. So I put the product behind x402: HTTP 402 "Payment Required", resurrected as a machine checkout. Here's exactly how it works, with the real shapes and flows. x402 from Coinbase turns the 402 status code into a payment handshake an agent can complete without human help: 402 with machine-readable payment terms in the body. X-Payment header carrying proof of payment. No accounts, no API keys, no OAuth dance for the buyer — the wallet is the identity, and the retry loop is the session. The 402 body isn't an error page. It's an offer. Here's the actual structure I return: { "x402Version": 1, "error": "Payment required", "accepts": { "scheme": "exact", "network": "base", "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", "payTo": "0xYourTreasuryWallet", "maxAmountRequired": "9000000", "maxTimeoutSeconds": 300, "resource": "https://scoutpacks-tunnel-1.loca.lt/buy/pack-25", "description": "25 verified B2B leads, JSON", "mimeType": "application/json" } } The fields that matter: payTo — your treasury wallet. The agent pays this address directly. maxAmountRequired — in the asset's base units. USDC has 6 decimals, so 9000000 = $9.00. This is the single most common bug I see: people write dollars and charge micro-cents. asset — the token contract above is USDC on Base . network — base here. Match your payTo wallet to a chain you actually monitor. scheme — exact means exact-amount settlement. resource — which endpoint the terms apply to. I also serve a machine-readable manifest at /.well-known/x402 so agents can discover the catalog and terms before touching a paid endpoint — cheaper than learning via 402s. Client side the agent's wallet code : python import requests URL = "https://scoutpacks-tunnel-1.loca.lt/buy/pack-25" resp = requests.get URL if resp.status code == 402: terms = resp.json "accepts" 0 Build + sign the USDC transfer per the scheme, then: payment payload = sign transfer terms base64, per the x402 spec resp = requests.get URL, headers={"X-Payment": payment payload} resp.raise for status leads = resp.json 200 — the goods Server side FastAPI-style : python @app.get "/buy/{pack id}" def buy pack id: str, x payment: str | None = Header default=None : pack = CATALOG pack id if x payment is None: return JSONResponse status code=402, content=payment terms pack verify onchain x payment, pack re-check amount, asset, recipient, settlement return deliver pack JSON leads: instant for the 25-pack Three things worth internalizing: maxTimeoutSeconds bounds how long the quote is valid; re-quote after it lapses. /.well-known/x402 manifest, and delivery should all read the same catalog object. If price lives in three places, it will drift. Raw HTTP is fine, but agents live in tool-calling land. The repo ships an MCP server with two tools: list packs — returns the catalog: pack sizes, prices, and exactly what each pack contains. No payment needed; this is the menu. buy pack pack id — runs the pay-and-retry flow above and returns the leads JSON. The MCP server reads the same catalog the 402 endpoint uses, so the menu and the checkout can never disagree. The pattern generalizes: list free, discoverable + buy 402-gated is a good shape for any agent-sold data product. Scout Packs is the live implementation of everything above: verified B2B lead packs for AI agents — 25 leads for $9, 50 for $15, 100 for $25. Every lead ships as JSON: company, contact, title, published email, plus the source URL it was verified against. list packs / buy pack : If you're selling anything to agents — data, compute, API access — stop minting API keys and start returning 402s. The wallet is the account.