# Comms

> Messages API for SMS and iMessage. Send and receive from your backend — the same way you'd use any messaging API.

## Docs

- [Agents](https://docs.osis.co/agents/overview.md): No-code agents on your line — optional when you use the Messages API.
- [Architecture](https://docs.osis.co/concepts/architecture.md): How inputs, intelligence, MCP, memory, and delivery fit together.
- [How Comms works](https://docs.osis.co/concepts/how-comms-works.md): Lines, keys, agents, and the Messages API — what each piece owns.
- [Errors & rate limits](https://docs.osis.co/guides/errors-and-rate-limits.md): Status codes, error bodies, and how to retry safely.
- [Idempotency](https://docs.osis.co/guides/idempotency.md): Make outbound sends safe to retry without double-texting customers.
- [Send your first message](https://docs.osis.co/guides/send-your-first-message.md): Request body, channels, idempotency, and what a 202 means on the wire.
- [Webhooks](https://docs.osis.co/guides/webhooks.md): Register HTTPS endpoints and receive message events without polling.
- [What is Comms?](https://docs.osis.co/index.md): A real phone line, an inbox, and a Messages API you call from your backend — SMS and iMessage without building the plumbing.
- [Authentication](https://docs.osis.co/messages-api/authentication.md): Bearer keys, scopes, rotation, and what Messages API credentials can access.
- [Create a webhook](https://docs.osis.co/messages-api/create-webhook.md): POST /api/v1/comms/webhooks — register an HTTPS endpoint for events.
- [List contacts](https://docs.osis.co/messages-api/list-contacts.md): GET /api/v1/comms/contacts — search people on your line.
- [List conversations](https://docs.osis.co/messages-api/list-conversations.md): GET /api/v1/comms/conversations — list threads on your line.
- [List delivery events](https://docs.osis.co/messages-api/list-events.md): GET /api/v1/comms/events — inspect outbound delivery attempts.
- [List messages](https://docs.osis.co/messages-api/list-messages.md): GET /api/v1/comms/messages — read message history on your line.
- [List webhooks](https://docs.osis.co/messages-api/list-webhooks.md): GET /api/v1/comms/webhooks — list registered webhook endpoints.
- [API overview](https://docs.osis.co/messages-api/overview.md): Base URL, versioning, auth summary, and the full Messages API map.
- [Send a message](https://docs.osis.co/messages-api/send-message.md): POST /api/v1/comms/messages — place an outbound SMS or iMessage on your line.
- [Upsert a contact](https://docs.osis.co/messages-api/upsert-contact.md): POST /api/v1/comms/contacts — create or update a person on your line.
- [Quickstart](https://docs.osis.co/quickstart.md): Create your Comms workspace, mint a Messages API key, send your first text, and optionally wire a webhook.