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

# Tool Calls

> Let your agent take action during a call

Tool calls let your agent **take action during a conversation**, like searching a knowledge base, scheduling a callback, transferring a call, or pulling data from your own system.

## What tools your agent can use

| Category               | What it does                                    | Examples                                           |
| ---------------------- | ----------------------------------------------- | -------------------------------------------------- |
| **Built-in tools**     | Ready to use on every agent.                    | `@endCall`, `@callMeLater`, `@waitForUserToReturn` |
| **Knowledge bases**    | Let the agent answer from your own documents.   | `@searchKnowledgeBase`                             |
| **Calendar tools**     | Book appointments during a call.                | Calendly, Cal.com, HubSpot                         |
| **Transfer tools**     | Move the call to another agent or number.       | `@transferCall:sales`                              |
| **Collect data tools** | Actively capture specific info from the caller. | `@collect_data:email`                              |
| **Custom tools**       | Connect to your own system mid-call.            | CRM lookup, account check                          |

## Add a tool to your agent

<Steps>
  <Step title="Open the Tools panel">
    In the agent builder, switch to the **Tools** panel in the sidebar to see every tool category available to your agent.

    <video loop muted playsinline style={{ width: '100%', cursor: 'pointer' }} onMouseEnter={(e) => e.currentTarget.play()} onMouseLeave={(e) => { e.currentTarget.pause(); e.currentTarget.currentTime = 0; }}>
      <source src="https://mintcdn.com/telli/oSe6yooA3Hku5xB9/onboarding-media/advanced_tool_calls/ToolCalls_01_NavigateTo.mp4?fit=max&auto=format&n=oSe6yooA3Hku5xB9&q=85&s=683728e468c88abd035a4d694f64606c" type="video/mp4" data-path="onboarding-media/advanced_tool_calls/ToolCalls_01_NavigateTo.mp4" />
    </video>
  </Step>

  <Step title="Pick a category and configure the tool">
    Choose the tool category that fits your use case (for example, a calendar connection or a custom tool) and fill in the configuration form.

    <video loop muted playsinline style={{ width: '100%', cursor: 'pointer' }} onMouseEnter={(e) => e.currentTarget.play()} onMouseLeave={(e) => { e.currentTarget.pause(); e.currentTarget.currentTime = 0; }}>
      <source src="https://mintcdn.com/telli/oSe6yooA3Hku5xB9/onboarding-media/advanced_tool_calls/ToolCalls_02_Configure.mp4?fit=max&auto=format&n=oSe6yooA3Hku5xB9&q=85&s=901fc27aaa51052038061e2ee9a6eba0" type="video/mp4" data-path="onboarding-media/advanced_tool_calls/ToolCalls_02_Configure.mp4" />
    </video>
  </Step>

  <Step title="Reference the tool in your prompt">
    In the prompt editor, click the tool in the Tools sidebar to insert it as `@toolName`. The sidebar always inserts the correct reference, so you don't have to remember the exact name.

    <video loop muted playsinline style={{ width: '100%', cursor: 'pointer' }} onMouseEnter={(e) => e.currentTarget.play()} onMouseLeave={(e) => { e.currentTarget.pause(); e.currentTarget.currentTime = 0; }}>
      <source src="https://mintcdn.com/telli/oSe6yooA3Hku5xB9/onboarding-media/advanced_tool_calls/ToolCalls_03_Insert.mp4?fit=max&auto=format&n=oSe6yooA3Hku5xB9&q=85&s=6ede6babab2f2e0dfcd44e44d48262a5" type="video/mp4" data-path="onboarding-media/advanced_tool_calls/ToolCalls_03_Insert.mp4" />
    </video>
  </Step>
</Steps>

<Note>
  In the prompt, you only define **when** the agent should use a tool, not **how the tool works technically**. The technical configuration lives in the agent settings.
</Note>

<Card title="Tool Calls" icon="bolt" href="/cookbooks/tool-calls/overview">
  Learn how to use tool calls to let your agent perform specific actions during a call.
</Card>

## Next Steps

<Card title="Advanced: Knowledge Bases" icon="book-open" href="/en/get-started/knowledge-bases">
  Give your agent access to your own information so it can answer questions during calls.
</Card>