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)