x402engine: Скилл для Pay-per-Call API

--- name: x402engine description: "Pay-per-call API gateway skill — calls 63 APIs (LLMs, image/video gen, flights, hotels, crypto, web search) via x402 micropayments. Each call costs $0.001-$0.60 in USDC/USDm, enforced by a local policy engine with spend caps." --- # x402engine Call 63 paid APIs via x402 micropayments. Each API call costs between $0.001 and $0.60, paid with USDC on Base/Solana or USDm on MegaETH. ## What this skill does This skill signs and submits stablecoin micropayments to call remote APIs on the user's behalf. It uses the EVM_PRIVATE_KEY environment variable to sign on-chain payment transactions. Each call deducts a small amount from the wallet. **Cost transparency:** When presenting results, include the cost of the call (e.g. "Bitcoin is $97,500 (cost: $0.001)"). If the user asks about spending, show full budget breakdown. ## Triggers - "what's the price of bitcoin" - "ethereum price" - "show me trending crypto" - "generate an image of a sunset" - "run this python code" - "transcribe this audio" - "wallet activity of vitalik.eth" - "ask gpt to explain x402" - "scrape this url" - "pin this to ipfs" - "resolve vitalik.eth" - "flights from JFK to LAX" - "search hotels in Paris" - "find cheap flights to Tokyo" - "how much budget is left" - "list available services" ## How it works 1. Fetch cached service catalog from discovery endpoint (default: https://x402engine.app/.well-known/x402.json). 2. Score query against 63 service descriptions to find best match. 3. Run policy preflight — check per-tx caps, daily caps, and recipient allowlist before signing. 4. Call service via @x402/fetch — handles 402 payment flow automatically. 5. Return structured data to the agent for natural-language presentation. ## Rules - Present results naturally. Include the cost of each call so the user knows what was spent. - If a payment fails due to insufficient funds, tell the user: "I need funds to access this service. Add USDC to your wallet to continue." - If no matching service is found, say so plainly — don't expose internal routing details. - Policy limits are authoritative — do not bypass spend caps or recipient allowlists. - Keep all decisions explainable with reason codes internally. ## Security ### Required credential - **EVM_PRIVATE_KEY** (required) — signs payment transactions. Use a dedicated wallet with limited funds — never your primary wallet. If not set, an ephemeral key is generated (no real funds, no payments possible). ### Optional configuration These environment variables are NOT required. They provide additional controls: - **EVM_PRIVATE_KEY_FILE** — alternative to EVM_PRIVATE_KEY; reads the key from a file instead of an env var. Use one or the other, not both. - **X402_POLICY_PATH** — path to a JSON policy file. Defines per-transaction caps, daily spending limits, and a recipient allowlist. Without this, no spending limits are enforced beyond the wallet's on-chain balance. When configured, the engine is fail-closed: if the file is missing or invalid, all payments are denied. - **X402_STATE_PATH** — path to a JSON file tracking daily spend and rate-limit state. Defaults to `.x402engine-state.json`. - **X402_DISCOVERY_URL** — override the service catalog URL (default: `https://x402engine.app/.well-known/x402.json`). Use a self-hosted catalog if you don't trust the default. - **X402_AUTOPREFLIGHT** — set to `false` to skip policy preflight checks. Enabled by default. - **X402_DISCOVERY_REFRESH_MS** — cache TTL for the service catalog in milliseconds. ### How payments work All payments go to the `payTo` address declared in the service catalog. The catalog is fetched from the discovery URL above. If you want to restrict which addresses can receive payments, configure a policy file with a recipient allowlist. ## Budget check When the user asks "how much budget is left" or similar: - Load policy and state files. - Show daily cap remaining per chain/asset if caps are enabled. - Show rate limit status. - Show wallet balance. ## Dependencies This skill requires Node.js and the following npm packages (declared in package.json): - `@x402/fetch` — x402 payment-aware fetch wrapper - `@x402/evm` — EVM payment scheme (Permit2 signatures) - `viem` — Ethereum client library Install with: `cd skills/x402engine && npm install` ## Reason Codes - `POLICY_MISSING`, `POLICY_INVALID` - `CHAIN_DENIED`, `ASSET_DENIED`, `RECIPIENT_DENIED` - `PER_TX_EXCEEDED`, `DAILY_CAP_EXCEEDED`, `RATE_LIMITED` - `ACTION_DENIED` - `SERVICE_NOT_FOUND` - `WALLET_UNDERFUNDED`