Only what changed since the last check

1. Poll from your loop

The first call saves a baseline and returns a cursor. Send it back next time and you get only the changes. The cursor advances only when a change is reported, so slow drifts add up and nothing slips through.

import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
// … register your wallet with registerExactEvmScheme(client, { signer })
let cursor;
setInterval(async () => {
  const r = await payFetch("https://agentsvc.io/api/v1/proxy/token-watch", {
    method: "POST", headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ token: "0x532f…42E4", chain: "base", cursor }),
  });
  const { data } = await r.json();
  cursor = data.cursor;
  if (data.changed) console.log(data.alert_level, data.summary);
}, 15 * 60_000);

2. Or let us poll and call your webhook

Top up credit once, create a watch with an interval and a webhook URL. We run the check on our side and POST a signed message only when something changed. Each check costs the normal price, charged from the credit.

# 1. credit token (x402, +10% bonus): POST /api/v1/proxy/credits-topup-1
# 2. create the watch
curl -X POST https://agentsvc.io/api/v1/watches \
  -H "Authorization: Bearer asvc_cr_…" -H "Content-Type: application/json" \
  -d '{"service":"page-watch","input":{"url":"https://example.com/pricing"},
       "interval_minutes":60,"webhook_url":"https://your-agent.example/hook"}'

Also available as MCP tools watch_create, watch_list and watch_delete at https://agentsvc.io/mcp (send the credit token as Authorization header). Details in the docs.