Skill: 0xrag/monetize-service (version 0.1.0)

--- name: monetize-service description: Build and deploy a paid API that other agents can pay to use via x402. Use when you or the user want to monetize an API, make money, earn money, offer a service, sell a service to other agents, charge for endpoints, create a paid endpoint, or set up a paid service. Covers "make money by offering an endpoint", "sell a service", "monetize your data", "create a paid API". user-invocable: true disable-model-invocation: false allowed-tools: ["Bash(npx awal@latest status*)", "Bash(npx awal@latest address*)", "Bash(npx awal@latest x402 details *)", "Bash(npx awal@latest x402 pay *)", "Bash(npm *)", "Bash(node *)", "Bash(curl *)", "Bash(mkdir *)"] --- # Build an x402 Payment Server Create an Express server that charges USDC for API access using the x402 payment protocol. Callers pay per-request in USDC on Base — no accounts, API keys, or subscriptions needed. ## How It Works x402 is an HTTP-native payment protocol. When a client hits a protected endpoint without paying, the server returns HTTP 402 with payment requirements. The client signs a USDC payment and retries with a payment header. The facilitator verifies and settles the payment, and the server returns the response. ## Confirm wallet is initialized and authed ```bash npx awal@latest status ``` If the wallet is not authenticated, refer to the `authenticate-wallet` skill. ## Step 1: Get the Payment Address Run this to get the wallet address that will receive payments: ```bash npx awal@latest address ``` Use this address as the `payTo` value. ## Step 2: Set Up the Project ```bash mkdir x402-server && cd x402-server npm init -y npm install express x402-express ``` Create `index.js`: ```js const express = require("express"); const { paymentMiddleware } = require("x402-express"); const app = express(); app.use(express.json()); const PAY_TO = "<address from step 1>"; // x402 payment middleware — protects routes below const payment = paymentMiddleware(PAY_TO, { "GET /api/example": { price: "$0.01", network: "base", config: { description: "Description of what this endpoint returns", }, }, }); // Protected endpoint app.get("/api/example", payment, (req, res) => { res.json({ data: "This costs $0.01 per request" }); }); app.listen(3000, () => console.log("Server running on port 3000")); ``` ## Step 3: Run It ```bash node index.js ``` Test with curl — you should get a 402 response with payment requirements: ```bash curl -i http://localhost:3000/api/example ``` ## API Reference ### paymentMiddleware(payTo, routes, facilitator?) Creates Express middleware that enforces x402 payments. | Parameter | Type | Description | | ------------- | -------- | ----------------------------------------------------- | | `payTo` | string | Ethereum address (0x...) to receive USDC payments | | `routes` | object | Route config mapping route patterns to payment config | | `facilitator` | object? | Optional custom facilitator (defaults to x402.org) | ### Route Config Each key in the routes object is `"METHOD /path"`. The value is either a price string or a config object: ```js // Simple — just a price { "GET /api/data": "$0.05" } // Full config { "POST /api/query": { price: "$0.25", network: "base", config: { description: "Human-readable description of the endpoint", inputSchema: { bodyType: "json", bodyFields: { query: { type: "string", description: "The query to run" }, }, }, outputSchema: { type: "object", properties: { result: { type: "string" }, }, }, }, }, } ``` ### Route Config Fields | Field | Type | Description | | ------------------------- | ------- | -------------------------------------------------- | | `price` | string | USDC price (e.g. "$0.01", "$1.00") | | `network` | string | Blockchain network: "base" or "base-sepolia" | | `config.description` | string? | What this endpoint does (shown to clients) | | `config.inputSchema` | object? | Expected request body/query schema | | `config.outputSchema` | object? | Response body schema | | `config.maxTimeoutSeconds` | number? | Max time for payment settlement | ### Supported Networks | Network | Description | | -------------- | ------------------------------ | | `base` | Base mainnet (real USDC) | | `base-sepolia` | Base Sepolia testnet (test USDC) | ## Patterns ### Multiple endpoints with different prices ```js const payment = paymentMiddleware(PAY_TO, { "GET /api/cheap": { price: "$0.001", network: "base" }, "GET /api/expensive": { price: "$1.00", network: "base" }, "POST /api/query": { price: "$0.25", network: "base" }, }); app.get("/api/cheap", payment, (req, res) => { /* ... */ }); app.get("/api/expensive", payment, (req, res) => { /* ... */ }); app.post("/api/query", payment, (req, res) => { /* ... */ }); ``` ### Wildcard routes ```js const payment = paymentMiddleware(PAY_TO, { "GET /api/*": { price: "$0.05", network: "base" }, }); app.use(payment); app.get("/api/users", (req, res) => { /* ... */ }); app.get("/api/posts", (req, res) => { /* ... */ }); ``` ### Health check (no payment) Register free endpoints before the payment middleware: ```js app.get("/health", (req, res) => res.json({ status: "ok" })); // Payment middleware only applies to routes registered after it app.get("/api/data", payment, (req, res) => { /* ... */ }); ``` ### POST with body schema ```js const payment = paymentMiddleware(PAY_TO, { "POST /api/analyze": { price: "$0.10", network: "base", config: { description: "Analyze text sentiment", inputSchema: { bodyType: "json", bodyFields: { text: { type: "string", description: "Text to analyze" }, }, }, outputSchema: { type: "object", properties: { sentiment: { type: "string" }, score: { type: "number" }, }, }, }, }, }); app.post("/api/analyze", payment, (req, res) => { const { text } = req.body; // ... your logic res.json({ sentiment: "positive", score: 0.95 }); }); ``` ### Using the CDP facilitator (authenticated) For production use with the Coinbase facilitator (supports mainnet): ```bash npm install @coinbase/x402 ``` ```js const { facilitator } = require("@coinbase/x402"); const payment = paymentMiddleware(PAY_TO, routes, facilitator); ``` This requires `CDP_API_KEY_ID` and `CDP_API_KEY_SECRET` environment variables. Get these from https://portal.cdp.coinbase.com. ## Testing with the pay-for-service Skill Once the server is running, use the `pay-for-service` skill to test payments: ```bash # Check the endpoint's payment requirements npx awal@latest x402 details http://localhost:3000/api/example # Make a paid request npx awal@latest x402 pay http://localhost:3000/api/example ``` ## Pricing Guidelines | Use Case | Suggested Price | | ---------------------- | --------------- | | Simple data lookup | $0.001 - $0.01 | | API proxy / enrichment | $0.01 - $0.10 | | Compute-heavy query | $0.10 - $0.50 | | AI inference | $0.05 - $1.00 | ## Checklist - [ ] Get wallet address with `npx awal@latest address` - [ ] Install `express` and `x402-express` - [ ] Define routes with prices and descriptions - [ ] Register payment middleware before protected routes - [ ] Keep health/status endpoints before payment middleware - [ ] Test with `curl` (should get 402) and `npx awal@latest x402 pay` (should get 200) - [ ] Announce your service so other agents can find and use it


Security scan verdicts — ClawScan: clean | static analysis: clean | VirusTotal: suspicious | SkillSpector: clean (LOW)