> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cartesia.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

Your Line agent needs audio input to work. Choose based on your use case.

## Telephony

Use [Cartesia Telephony](/line/integrations/telephony/phone-numbers) for managed phone numbers. Cartesia provisions numbers and handles the telephony infrastructure for inbound and outbound use cases.

You can also use your own telephony stack by connecting to the [Calls API](/line/integrations/calls-api).

<Note>
  Bringing your own phone numbers or CCaaS provider is on the roadmap.
</Note>

## Web and Mobile Apps

Use the [Calls API](/line/integrations/calls-api) to stream audio between your application and the agent via WebSocket.

```javascript theme={null}
const ws = new WebSocket(`wss://api.cartesia.ai/agents/stream/${agentId}`);
```

This option works great for:

* Web applications with browser microphone access
* Mobile apps with native audio capture

## Pricing

| Feature                  | Price per Minute | Notes                                 |
| ------------------------ | ---------------- | ------------------------------------- |
| Agent Calling            | \$0.06           | Base rate for all voice agent calls   |
| Telephony (add-on)       | +\$0.014         | Additional when using managed numbers |
| **Total with Telephony** | **\$0.074**      | Combined cost for phone-based calls   |

View your usage and remaining Voice Agent credits on the [Subscription](https://play.cartesia.ai/subscription) page.