x402 Payments Skill — Stellar Edition

The first production-ready x402 payments skill for AI agents on Stellar.

Teaches Claude Code, Codex, Cursor, Windsurf, and Gemini CLI how to build x402 payment infrastructure on Stellar — server middleware, agent payment clients, and facilitator routing via OZ Channels.

---

What it does

One install. Your AI agent knows how to:

• Monetize any API with x402 middleware (Express, Hono, Next.js) on Stellar
• Call paid endpoints with automatic 402 payment handling
• Deploy on Stellar with USDC (Soroban SAC) — fee-free for clients
• Route payments through OZ Channels facilitator — verify, settle, supported
• Generate a full testnet runbook for end-to-end testing

Quick Install

curl -sSL https://raw.githubusercontent.com/ASGCompute/x402-payments-skill/main/install.sh | bash

Auto-detects Claude Code, Codex CLI, and Cursor. Installs the skill to the right location.

Live Examples

Two ready-to-clone projects in examples/:

Seller: Stellar x402 Server

An Express API charging $0.001/request in USDC on Stellar testnet.

cd examples/stellar-x402-server && npm install && npm run dev

Buyer: Agent Payment Client

Node.js script that calls paid endpoints — handles 402 challenges, signs Soroban auth entries, pays USDC automatically.

cd examples/stellar-x402-client && npm install && npm start

What's Inside the Skill

The skill teaches your AI agent a decision tree:

User asks about x402 / paid APIs / agent payments on Stellar
│
├─ Are you the SELLER or BUYER?
│  ├─ Seller → Express middleware setup with @x402/express
│  └─ Buyer → Client fetch wrapper with Soroban signing
│
├─ Which NETWORK?
│  ├─ Testnet → stellar:testnet + OZ Channels testnet facilitator
│  └─ Mainnet → stellar:pubnet + production facilitator
│
├─ FACILITATOR setup?
│  ├─ OZ Channels → https://channels.openzeppelin.com/x402/testnet
│  └─ Custom → self-hosted facilitator on Fly.io
│
└─ Need a TESTNET RUNBOOK?
   ├─ No → Basic x402 is enough
   └─ Yes → Full e2e flow: fund → challenge → sign → verify → settle

Full reference docs for every path: Stellar Soroban, Facilitator routing, and all relevant npm packages.

Install

Claude Code (Manual)

git clone https://github.com/ASGCompute/x402-payments-skill.git
cp -r x402-payments-skill/x402-payments ~/.claude/skills/

Codex CLI

git clone https://github.com/ASGCompute/x402-payments-skill.git
cp -r x402-payments-skill/x402-payments ~/.codex/skills/

Cursor / Windsurf

Copy .cursorrules into your project root:

cp x402-payments-skill/.cursorrules ./

Per-project (shared via git)

cp -r x402-payments-skill/x402-payments .claude/skills/

What's inside

x402-payments/
├── SKILL.md                    # Main decision tree + quick starts
└── references/
    ├── stellar.md              # Complete Stellar setup (Soroban, auth-entries, OZ Channels)
    ├── facilitator.md          # Facilitator routing (verify/settle/supported)
    └── packages.md             # All npm packages
examples/
├── stellar-x402-server/        # Express server with x402 middleware
└── stellar-x402-client/        # Agent payment client

x402 Protocol

x402 is an open payment protocol by Coinbase using HTTP 402 status codes. Any API can charge per-request in USDC — no API keys, no subscriptions, no accounts. Works for humans and AI agents.

Stellar Advantage

• Fee-free settlement — facilitator covers all Stellar network fees (~$0.00001/tx)
• Sub-5s finality — Stellar settles in 1 ledger close (~5 seconds)
• Soroban smart contracts — auth-entry signing, no full transaction signing required
• SEP-41 tokens — USDC, PYUSD, USDY all supported via standard interface

Built by

ASG Card — Instant virtual MasterCard cards for AI agents, paid via x402 on Stellar.

ASG Compute — GPU infrastructure and AI agent services.

License

MIT