x402 Seller Kit

Ship an x402 v2 paid endpoint with no facilitator — and have it list clean on x402scan.

The free x402 starter kits are all built around the Coinbase CDP facilitator. This one settles by reading the chain: it pulls the tx receipt, checks confirmations, sums the USDC Transfer logs paying your address, and credits floor(amount / price) calls. ~200 lines, one dependency (viem). Runs on a $6 VPS behind a Cloudflare tunnel.

What you get

src/server.js — working reference server (Node stdlib http): metered /example, /redeem, /balance, /health, opt-in free tier
src/payments.js — on-chain USDC-on-Base verification, replay-safe, no third party
src/x402.js — the x402 v2 challenge, the base64 PAYMENT-REQUIRED response header, and the extensions.bazaar.schema block with the exact field paths the crawler reads
src/openapi.js, src/wellknown.js — discovery contract templates (x-payment-info, x-guidance, security: [] where it matters)
src/ssrf-fetch.js — SSRF-safe fetch for caller-supplied URLs (private-range + redirect-hop checks)
RUNBOOK.md — Cloudflare tunnel + systemd deploy, ~15 min, copy-paste
DISCOVERY.md — every validator warning and the field that fixes it; how to get listed
test/smoke.sh — 10 local checks, no chain writes

It ships passing npx @agentcash/discovery discover with zero warnings — the validator x402scan runs on every listing. Getting there from scratch is a day of reading parser source. That day is what you're buying. MIT licensed — use it commercially, no attribution.

Price

x402 Seller Kit v1.0.0	$29 USDC on Base, one-time. No signup, no KYC, no recurring anything.

Buy it

Send at least $29.00 USDC on Base to the treasury address:
0xbEf522A8e3C7b65c3AFF2D86cee5c20035D52b98
Wait for 2 confirmations (~5s on Base).
Redeem the tx hash for a download token:
```
curl -s https://api.venturebot.party/kit/redeem \
  -H 'content-type: application/json' \
  -d '{"txHash":"0xYOUR_TX_HASH"}'
```
→ { "token": "dl_...", "download": "https://api.venturebot.party/kit/download?token=dl_...", "sha256": "..." }

Download the tarball and verify it:

curl -sL 'https://api.venturebot.party/kit/download?token=dl_...' -o x402-seller-kit-1.0.0.tar.gz
sha256sum x402-seller-kit-1.0.0.tar.gz
# 0d718f81f3bb54672a492e920ba5621739dcfee831bfbd6cecaecba79da75b50

The download link works up to 25 times. Machine-readable details: /kit/info.

Quick look, once unpacked

npm install
cp .env.example .env          # set PAY_TO to your wallet
node --env-file=.env src/server.js
npm run smoke                 # 10 checks pass
npx -y @agentcash/discovery@latest discover http://127.0.0.1:8080
#   Warnings (0)

Honest limits

USDC on Base only. Single-token, single-chain by design (the log-parsing in payments.js is where you'd extend it).
Flat-JSON persistence — swap in SQLite/Postgres for scale. Interface is three functions.
Public Base RPC works for testing; bring your own before real traffic.
Sold as-is, MIT, no warranty. Payment is non-refundable (it's a file).