# SMS

> Two-way texting on the business's number: the 5-second lead text, missed-call text-backs, reminder cadences, and the one-time A2P registration that makes it deliverable.

The SMS service gives the business two-way texting: customers text the number and the AI answers; workflows and [campaigns](/docs/campaigns/overview) text out. The single highest-value use is **speed to lead** — a form submission or missed call gets a text within seconds, while the customer is still deciding.

## A2P registration (required)

US carriers require every business texting from an application to register (A2P 10DLC). Untracked traffic gets filtered — messages silently vanish. OpenAgent runs the registration for you:

1. **Fill in the business profile** — Legal name, EIN, address, website, and how customers opt in. The service's **Compliance** page lists exactly what's missing.
2. **Submit for registration** — One click (or the [MCP tool](/docs/mcp/tools) `register_sms_compliance`). Approval typically takes a few days — start early.
3. **Assign a number** — Once approved, attach a texting-enabled number to the service. Until then the service runs in sandbox so you can build and test workflows.

> **START REGISTRATION ON DAY ONE:** It's the only part of setup with a multi-day wait. Everything else in OpenAgent is live in minutes; do this first and build while it's approving.

## What SMS is used for

- **The 5-second lead text** — form submitted → SMS within seconds. 78% of customers hire the first responder.
- **Missed call → text back** — "Sorry we missed you — reply here and we'll get you booked." The AI handles the reply.
- **Reminders** — booking confirmations, day-before and morning-of texts that cut no-shows 30–50%.
- **Two-way AI conversations** — "text us your order"; the SMS agent takes it from there.
- **Campaigns** — reactivation and seasonal sends to [audiences](/docs/campaigns/audiences), with STOP and quiet hours enforced.

## Compliance behavior

- **STOP** unsubscribes the contact everywhere, instantly — one suppression list workspace-wide.
- **Quiet hours** hold non-urgent sends until morning.
- **DND on the contact** blocks the channel no matter which workflow or campaign tries. See [DND & suppression](/docs/crm/dnd).