Metered API Marketplace

Provide a production-lean template for: OpenClaw Skill → Public API Endpoint → Usage Metering → Crypto Payment Gateway → BTC/ETH wallets.

This skill ships a runnable reference server (Fastify + SQLite) that: - Accepts structured JSON input - Performs a high-value transformation (pluggable “transformers”) - Returns structured JSON output - Enforces signed API key auth - Checks prepaid balance, deducts per call, and logs usage - Accepts payment webhooks (Coinbase Commerce / BTCPay Server style) - Applies a 2.5% platform fee in the ledger (fee addresses configurable)

Workflow (do this in order)

1) Pick the productized capability (the thing people pay for)

Choose ONE transformer that is: - high leverage (makes/keeps money) - repeatable (called often) - defensible (data, heuristics, workflow, or automation — not “generic summarization”)

Good defaults: - revenue/offer optimizer - ad copy optimizer - lead scoring - contract risk flags

If unclear, start with the included revenue-amplifier transformer and replace it later.

2) Run the reference server locally

Use the bundled server in scripts/server/.

Typical run: - cd scripts/server - npm install - cp .env.example .env and edit - npm run dev

Set flat launch pricing in .env: - COST_CENTS_PER_CALL=25 # $0.25/call

3) Create an API key

Use scripts/server/admin/create_key_pg.js (or the admin HTTP endpoint) to create a key and starting balance.

4) Integrate from an OpenClaw skill / agent

Call the public endpoint with: - x-api-key - x-timestamp (unix ms) - x-signature = hex(HMAC_SHA256(api_secret,${timestamp}.${rawBody}))

5) Add real payments

Wire a payment processor webhook to /v1/payments/webhook/:provider.

Providers are adapter-based: - start with “manual” credits (admin script) - then add Coinbase Commerce or BTCPay Server

6) Ship

Deploy behind TLS (Cloudflare / Fly.io / Render / AWS / GCP). Put rate limiting at the edge + in-app.

Bundled resources

scripts/server/

Runnable reference implementation: - Fastify API server (long-running) - Postgres ledger (balances, usage, credits) - Signed API key auth - Rate limiting + basic anti-abuse - Webhook endpoint(s)

scripts/nextjs-starter/

Vercel-ready Next.js API implementation: - Serverless API routes (no listen()) - Postgres ledger (Supabase Transaction Pooler recommended) - Same auth + pricing + webhook concepts

references/

Read only when needed: - references/api_reference.md – endpoint contracts + auth/signing - references/billing_ledger.md – pricing, fee logic, idempotency - references/providers.md – provider adapters (Coinbase/BTCPay patterns)