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

# API reference

> Build server integrations, receive events and connect AI tools, web embeds and mobile apps to Tars.

## What you can build

Start conversations, send WhatsApp messages, manage end-user records, trigger campaigns and place or inspect calls through one API.

## Ways in

| Surface | Start here |
| - | - |
| API keys | [Authentication](https://hellotars.com/docs/developer/authentication.md) |
| MCP connections | [Connect AI tools](https://hellotars.com/docs/developer/mcp.md) |
| Webhooks | [Receive events](https://hellotars.com/docs/developer/webhooks/index.md) |
| Requests your agents send | [Agent requests](https://hellotars.com/docs/developer/agent-requests.md) |
| Web embed | [Script and configuration](https://hellotars.com/docs/developer/embed/script-and-config.md) |
| Mobile | [WebView bridge](https://hellotars.com/docs/developer/mobile/webview-bridge.md) |

## Base URL and regions

Every request goes to the base URL for your organization's region. Each key works at its organization's base URL. When the organization moves region, its keys move with it. Pick the matching row.

<table>
  <thead>
    <tr><th>Region</th><th>Base URL</th></tr>
  </thead>

  <tbody>
    {api.regions.map((r_0) => (
            <tr key={r_0.id}>
              <td>{r_0.flag} {r_0.label}</td>
              <td><code>{r_0.base}</code></td>
            </tr>
          ))}
  </tbody>
</table>

Code samples on these pages use the United States base URL. The dashboard shows the right base URL for your organization beside your API keys.

## Where to go next

* [Requests and limits](https://hellotars.com/docs/developer/requests.md)
* [Errors and retries](https://hellotars.com/docs/developer/errors.md)
* [Conversations](https://hellotars.com/docs/developer/api/conversations.md) and [messages](https://hellotars.com/docs/developer/api/messages.md)
* [Contacts](https://hellotars.com/docs/developer/api/contacts.md) and [campaigns](https://hellotars.com/docs/developer/api/campaigns.md)
* [Calls](https://hellotars.com/docs/developer/api/calls.md), [agents](https://hellotars.com/docs/developer/api/agents.md) and [phone numbers](https://hellotars.com/docs/developer/api/phone-numbers.md)
* [Webhook destinations](https://hellotars.com/docs/developer/api/webhooks.md)
* [Identity signing](https://hellotars.com/docs/developer/embed/identity-signing.md)


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