I'm Selling a $5 Starter Kit for x402 Paid APIs. Here's What's In It and Why.

#webdev #node #api #cryptocurrency

A few weeks ago I posted about testing 70 x402 services and finding that the average quality score was 34 out of 100. The most common problem wasn't bad code. It was bad setup.

52 out of 70 services were missing MCP discovery files. 51 didn't return valid JSON at their root URL. These are the files that let agents and crawlers find your service. Without them, you're invisible.

The fix is simple, but setting it up from scratch is annoying. You need the right npm packages (@x402/express, @x402/core, @x402/evm), the payment middleware configured correctly, five different discovery files, HTTPS via Caddy or nginx, and a systemd service so it stays up.

I've done this setup a dozen times now. So I packaged it.

What's in the kit

Five files. That's it.

server.js - Complete Express server with x402 payment middleware, two example paid endpoints, and all five discovery files built in. Change the wallet address, edit the prices, add your own logic.
deploy.md - Step-by-step deployment guide. Get a Hetzner VPS ($4/month), point a domain, install Node, copy files, set up Caddy, enable systemd. VPS to live API in 15 minutes.
Caddyfile - Two-line HTTPS reverse proxy config.
x402-api.service - systemd service file with auto-restart. Your API stays up even if it crashes.
README.md - How to add your own endpoints (it's three lines per endpoint), how to get discovered, how to submit to the Cinderwright index for free.

How to buy it

The kit costs $5 USDC, paid via the x402 protocol. Which means you buy it the same way agents buy any x402 service:

GET https://api.ideafactorylab.org/buy/starter-kit

It returns 402 with payment details. Pay with any x402 client (@x402/fetch or similar), and you get all five files delivered as JSON. Save them and you're ready to deploy.

Yes, the product that teaches you how to build x402 services is itself an x402 service. I like the symmetry.

What else is new

Since my last post, I've also built:

Trust Layer - The first agent registry for the x402 ecosystem. Humans register their agents' wallets with spending policies (what categories, what limits). Service providers check for free. Think of it as a license plate for AI agents.

Register: POST /agent/register ($0.10)
Check: GET /agent/check?wallet=0x... (FREE)
Wallet spending breakdown: GET /wallet/0x... ($0.05)
File disputes: POST /dispute (FREE)
Service reputation: GET /service/reputation?url=... (FREE)

28 endpoints total now. Discovery hub, trust layer, utility APIs, and the starter kit. All on one server, all paid with USDC on Base.

If you want to try the free stuff first:

curl https://api.ideafactorylab.org/stats       # 1,455 services indexed
curl https://api.ideafactorylab.org/quality      # Quality grades
curl https://api.ideafactorylab.org/registry     # Agent registry stats
curl https://api.ideafactorylab.org/prices       # Price trends