# Sinch Functions & CLI

> **Sinch Functions is currently in beta.** You can build, deploy, and run real traffic today. APIs and capabilities may evolve during the beta — we will call out breaking changes in release notes.


Two things in one toolchain:

- **Sinch CLI** — the developer command line for every Sinch API. Rent phone numbers, send SMS and fax, manage SIP trunks, configure voice apps, manage secrets. All from your terminal.
- **Sinch Functions** — a serverless runtime where you write a function, deploy it, and Sinch routes live traffic (voice calls, WhatsApp messages, SMS) to your code.


The Sinch CLI is how you interact with both.

## Pick your path

- **[New to Sinch?](/docs/functions/concepts/overview)** — A one-page overview of what these things are and how they relate.
- **[Install the CLI](/docs/functions/cli/installation)** — Get `sinch` on your machine and log in.
- **[Your first Function](#)** — Deploy a voice IVR in five minutes.
- **[Glossary](/docs/functions/concepts/glossary)** — ICE, ACE, SVAML, Voice App, Conversation App in plain English.


## What you can build with Functions

| Use case | What it does |
|  --- | --- |
| Voice IVR | Interactive menus with DTMF input and text-to-speech |
| SMS responder | Reply to inbound SMS with dynamic content |
| Call routing | Route calls based on caller, time, or external data |
| AI voice agent | Connect calls to a speech AI pipeline via ElevenLabs or similar |
| Number masking | Proxy calls between parties without exposing real numbers |
| Conversation bot | Handle WhatsApp, Messenger, SMS via the Conversation API |


## What you can do with the CLI

| Workflow | Command |
|  --- | --- |
| Rent a phone number | `sinch numbers available rent` |
| Send an SMS | `sinch conversation send` |
| Send a fax | `sinch fax send` |
| Manage SIP trunks | `sinch sip trunks` |
| Deploy a function | `sinch functions deploy` |
| Stream function logs | `sinch functions logs --follow` |
| Store a secret | `sinch secrets add` |


## Two runtimes, one mental model

Functions runs your code on either runtime with full feature parity.

|  | Node.js | C# |
|  --- | --- | --- |
| Language | TypeScript / JavaScript | C# / .NET 9+ |
| Package | `@sinch/functions-runtime` | `Sinch.Functions.Runtime` |
| Mental model | Like Express | Like ASP.NET MVC with controllers |


If you know Express or ASP.NET MVC, you already know 90% of the runtime. The rest is conventions for how Sinch maps URLs to your handlers.

## Where to go next

- [Concepts & architecture](/docs/functions/concepts/overview)
- [Install the CLI](/docs/functions/cli/installation)
- [Quickstart for Functions](#)
- [CLI command reference](/docs/functions/cli/overview)
- [Runtime cheat sheets](/docs/functions/reference/function-context)