Publish an API

This page covers end‑to‑end setup using the monorepo (SDK + Express + CLI). You can adapt to any framework as long as you produce the same JSON.

1) Install


# From the sylan-provider repo root
pnpm i
pnpm -w build
 
# Create a local config
npx sylan-provider init
# → creates sylan.config.json (edit it)

sylan.config.json fields:


{
  "chainId": 80002,
  "rpcUrl": "https://rpc-amoy.polygon.technology",
  "consensusAddress": "0x81B78B79775C04F5c30DfBC17d9710EA5C3CB166",
  "registryAddress": "0xda70c416Ef9fbc86719AfD9aEDb0EE43263aCd97",
  "apiId": "0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
  "providerSignerKey": "0xPROVIDER_SIGNER_PRIVATE_KEY",
  "ttlMs": 0,
  "seqStrategy": "monotonic"
}

apiId: bytes32 identifier of your listed API in AccessRegistry
providerSignerKey: the EOA private key corresponding to the provider signer on-chain
ttlMs: 0 = no TTL; otherwise a positive millisecond window for freshness
seqStrategy: monotonic (always increment) or hash-change (increment only when payload changes)

2) Wrap your endpoint (Express)


import { createServer } from '@sylan/provider-express'
 
const { app, listen } = createServer({
  apiId: '0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef',
  consensus: '0x81B78B79775C04F5c30DfBC17d9710EA5C3CB166',
  chainId: 80002,
  signKey: '0xPROVIDER_SIGNER_PRIVATE_KEY',
  ttlMs: 60000,
})
 
app.get('/weather', async (_req, res, next) => {
  // your payload — any JSON-serializable object
  const data = { city: 'Doha', tempC: 39, date: new Date().toISOString() }
  res.locals.data = data
  next() // hand off to Sylan middleware → hashes, signs, replies
})
 
listen(3000)

Response shape (produced by the middleware)


{
  "data": { /* your payload */ },
  "snapshot": {
    "apiId": "0x…",
    "seqNo": "123",
    "providerTs": "1724700000000",
    "ttl": "60000",
    "contentHash": "0x…"
  },
  "providerSig": "0x…",
  "pointerURI": null
}

The middleware persists sequence numbers per apiId in ~/.sylan/seq.json (override via storageDir).

3) Serve with the CLI (optional)


# Reads sylan.config.json and runs the built‑in server on :3005
npx sylan-provider serve

4) Verify your on‑chain listing

Before going public, confirm your API is Active in AccessRegistry:


npx sylan-provider health
# → prints { chainId, registry, apiId, active: true/false }

If inactive, finish your listing & activation in the dashboard, then retry.