Add two-way iMessage to your application

Start with a send and an inbound reply

Comms by Osis is a hosted API for sending and receiving iMessage and SMS (eligible RCS) from your own application. One POST to /api/v1/comms/messages sends a message; replies arrive as signed webhooks. You do not run a Mac.

Free starts on a shared line with 100 messages a day; a dedicated number is $200/month with $0 setup.

Create a scoped API key, pick a test recipient who has agreed to hear from you, and send. The API accepts a message before the recipient has necessarily received it, so save the returned message ID and subscribe to delivery and inbound events.

const response = await fetch("https://osis.co/api/v1/comms/messages", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.COMMS_API_KEY}`,
    "Content-Type": "application/json",
    "Idempotency-Key": "appointment-4242-confirm"
  },
  body: JSON.stringify({
    to: process.env.COMMS_TEST_TO,
    body: "Your appointment is confirmed.",
    channel: "auto"
  })
});
if (!response.ok) throw new Error(`Comms returned ${response.status}`);
const result = await response.json();
console.log(result.message.id); // acceptance is not delivery

• Messaging quickstart
• Send-message request and response

What can the Comms iMessage API do?

Beyond sending text and media, the API covers the parts of iMessage that make a conversation feel like one. Each item below has its own endpoint in the API reference.

• API reference
• Hosted iMessage MCP server

Messaging channels have different capabilities

Auto routing selects an available channel for the sending line and recipient, moving to another channel only after a confirmed pre-send rejection. RCS fallback supports plain text. An uncertain result does not trigger another send. An explicit channel never falls back.

Acceptance is not delivery. Delivery and read events depend on the channel, line, recipient, and available receipts. SMS does not provide read receipts.

• Check recipient capabilities
• RCS requirements and limits

Phone-number iMessage is distinct from Apple Messages for Business

Comms provides hosted phone-number messaging infrastructure. Apple Messages for Business uses a verified business identity and a different onboarding and conversation model.

Do not assume a phone-number integration is an Apple-approved business channel, or that business-channel features are available through the same endpoint.

You do not operate a Mac server for this integration, but you do depend on Comms, its infrastructure and supported channels. Evaluate number control, delivery behavior and support before committing a production workflow.

• Compare Twilio and Apple business messaging

Receive replies reliably

Verify X-Osis-Signature against the exact request bytes, persist the event ID and payload, acknowledge quickly, then process asynchronous work. Several events can share a recordId, so deduplicate the event id rather than the message ID.

The runnable example uses a durable SQLite inbox and explicit line-to-tenant mapping. It includes signed webhook tests, duplicate handling, human ownership and a local send simulator. A multi-instance production deployment needs a shared database or queue.

• Download the runnable Node.js example and tests
• Verify webhook signatures and deduplicate events
• Retry safely with an idempotency key

Dedicated numbers and production access

API line claiming requires workspace approval and available inventory. A denied claim returns line_claim_not_allowed; unavailable inventory returns no_available_line.

Porting requires approval and a supported number. Confirm port-in, port-out, geographic availability, fees, and timing before planning a migration. You can cancel replacement setup before submitting the transfer; a submitted transfer cannot be canceled from the setup panel.

Free and Plus use shared lines. Dedicated is $200/month with $0 setup; available area codes and numbers depend on inventory. Confirm geographic support, channel readiness, capacity and porting terms before promising an instant number to every SaaS customer.

• One messaging number per SaaS customer
• Plans and production questions

What is available today

Payment requests use checkout links only when the global Payments product and workspace payments are enabled and merchant requirements are met. Native in-thread Apple Pay is coming soon; checkout links are not native Apple Pay in Messages.

For a current capability summary, use the product facts page and endpoint documentation. MCP is available as a hosted connection; it is not a future-only integration.

• Reviewed product facts and release notes
• Hosted messaging MCP setup