x402 Payment Gating Plugin — monetize any API with USDC micropayments

[plagtech]

x402 Payment Gating Plugin — Turn any API into a paid API with USDC micropayments

Hey Kong community 👋

I built a JavaScript PDK plugin that adds x402 payment gating to any Kong route or service. One config, no code changes to your upstream APIs.

The problem: API monetization today means integrating billing platforms, managing API keys, and building subscription logic. For AI agents and machine-to-machine traffic, traditional auth-based billing doesn't work — agents need to pay per call, instantly, with no signup.

The solution: The x402 protocol (HTTP 402 Payment Required) lets clients pay for API access with USDC stablecoin micropayments. This plugin brings that to Kong.

How it works:

Client → Kong (x402 plugin) → Your API
         │
         ├─ No payment header   → 402 + payment requirements JSON
         ├─ Valid payment        → forward request to upstream
         └─ Invalid payment     → 402 + error details

Configure per route:

curl -X POST http://localhost:8001/services/my-api/plugins \
  --data "name=x402-payment" \
  --data "config.price=0.01" \
  --data "config.token=USDC" \
  --data "config.chain=base" \
  --data "config.facilitator=0xYourAddress"

That's it. Any request without a valid payment gets a 402 with everything the client needs to pay. Agents and clients that support x402 handle payment automatically.

Why this matters for Kong: Kong already has a Monetization plugin category. AI agent traffic is growing fast, and agents need a way to pay for API access without API keys or subscriptions. x402 is becoming the standard for this — Stripe recently added x402 support on Base. This plugin lets any Kong user tap into that.

Repo: https://github.com/plagtech/kong-plugin-x402

Docker quickstart included — docker compose up and you have a working demo.

Built with the JavaScript PDK. Payment verification routes through Spraay Protocol's x402 gateway (https://gateway.spraay.app). Would love feedback from the community, and happy to explore getting this on the Plugin Hub.