Text messages from your own numbers.

// 1. Send from one of your organization's numbers.
const { data: sms, error } = await coss.sms.send(
  {
    from: "+14155550123",
    to: "+14155550199",
    body: "Your Acme order #1042 has shipped.",
  },
  { idempotencyKey: "order-1042-shipped" },
);
if (sms) console.log(sms.status, sms.segments, sms.encoding); // "queued", 1, "gsm7"

// 2. Follow delivery and replies through webhooks.
const event = await verifyWebhook(await request.text(), request.headers, secret);
if (event.type === "sms.received" && event.data.received_sms_id) {
  const { data: reply } = await coss.sms.received.get(event.data.received_sms_id);
  console.log(reply?.from, reply?.body);
}

Sends return 202 with status: "queued", and a background worker hands the message to the carrier. Retrying with the same idempotency key returns the first message instead of sending a second one. See sending SMS and the API reference.

Each environment keeps its own SMS suppression list. A send to a suppressed number fails at once with suppressed and is never handed to a carrier or billed. Numbers that can't receive SMS and carrier-refused opt-outs are added automatically, and you can add your own with coss.sms.suppressions.add().

A sample of live messages is screened for spam, phishing, malware and fraud before it is sent, like email. coss.com also measures each organization's opt-out rate and carrier filtering rate over a rolling window: high rates bring a warning, then a suspension of live sending, before carriers start blocking your numbers. Live keys can text the same number at most 10 times an hour, which stops a looping form or a pumping attack there.

Sandbox (coss_test_…) keys accept any from number and skip the number, country and plan checks. Send to +15005550006 and the message is delivered, to +15005550004 and the carrier filters it, to +15005550009 and the recipient has opted out, to +15005550008 and a reply arrives in the same environment. Statuses, events, webhooks and logs behave as in live environments, and nothing is sent or billed. See testing SMS.

Live SMS needs a paid plan; Free organizations send in sandbox environments. Failed, suppressed and canceled messages cost nothing. Every country's rate per segment, sent and received, is on the pricing page.