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

# Ultra-low latency agents

> What an Ultra-low latency (Enhanced) agent is, how it differs from a Premium Voice agent, and what each tab of its editor does.

[Open the AI Agents page in Callin.io](https://app.callin.io/agents)

## What is an Ultra-low latency agent

An **Ultra-low latency** agent answers almost instantly, so the conversation feels smooth and live. It's one of the **Agent stack** options you choose when you create an agent. In the agents list, these agents show the **Enhanced** label.

Ultra-low latency agents are also the only ones that can work together in a [Squad](https://support.callin.io/Create-AI-Agent/Squads.md), where agents hand off the call to each other.

> [!NOTE]
>
> This page covers what is different in an Ultra-low latency agent. For everything the two stacks share, it links to the [AI Agents](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md) page, which describes agents created with the **Premium Voice** stack.

## Ultra-low latency vs. Premium Voice

The editor of an Ultra-low latency agent is simpler. It has eight tabs: **Agent**, **Knowledge Base**, **Conversation**, **Analytics**, **Tools**, **Call Action**, **Goals**, and **Advanced**.

| | Premium Voice | Ultra-low latency |
| - | - | - |
| **Workflow** tab | Yes | No |
| **Website widget** tab | Yes | No |
| **Goals** tab | No | Yes |
| Choose the AI model (**AI Intelligence (LLM)**) | Yes | No |
| **Call Direction** setting | Yes | No |
| Additional voices | Yes | No |
| System tools | Seven | Two: **Smart Hang-up** and **Voicemail Intelligence** |
| **Inbound fallback** number | No | Yes |
| Can join a **Squad** | No | Yes |

> [!TIP]
>
> If you can't find a setting described on the [AI Agents](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md) page, check the agent's stack first. Many of those settings only exist in Premium Voice agents.

## Create an Ultra-low latency agent

**Step 1**

Go to **AI Agents** and click **Create Agent**.

**Step 2**

Choose how to start (from scratch, from a template, or from one of your organization's templates), as described in [Create a new agent](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#create-a-new-agent).

**Step 3**

In **Agent stack**, select **Ultra-low latency**.

**Step 4**

Click **Create Agent**. The agent opens in its editor, on the **Agent** tab.

Saving works the same as in any agent: when you change something, the **You have unsaved changes** bar appears with **Save** and **Clear**. To try the agent, use **Test AI agent** at the top right.

## Agent

The **Agent** tab holds what the agent says and how it sounds.

![The Agent tab with the Conversation Prompt editor and the time zone on the left, and the Voice and Language panels on the right.](https://mintcdn.com/lechusai/Bm4nSAiwh1gnk2Oe/images/ultra-low-latency-agent.png?fit=max\&auto=format\&n=Bm4nSAiwh1gnk2Oe\&q=85\&s=54cd19ebcabf04a70111e080b03addae)

Screenshot: the Agent tab of an Ultra-low latency agent.

* **Conversation Prompt** — the agent's instructions: its goals and the rules it must follow. Under the editor, **Add Variables** inserts variables and the menu on the right sets the agent's time zone.
* **Greeting Message** — the very first words the agent says.
* **Dynamic Variables** — placeholders like `{{agent_name}}` that are replaced with real values during the call.
* **Voice** — the agent's voice. Click it to choose another voice and to adjust **Speed** and **Volume**.
* **Language** — the default language. Use **Add Additional Languages** so the agent can switch language mid-conversation.

The prompt, greeting, and variables work as described in [Section 1: Agent](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#section-1%3A-agent).

> [!NOTE]
>
> There's no **Call Direction** setting in this tab. The agents list shows these agents as **Inbound & Outbound**.

## Knowledge Base, Conversation, and Analytics

These three tabs work the same as in a Premium Voice agent:

* **Knowledge Base** — the documents the agent can use to answer questions. See [Section 3: Knowledge Base](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#section-3%3A-knowledge-base).
* **Conversation** — the agent's calls, with filters. The **Squad** filter finds the calls handled by a squad. See [Section 4: Conversation](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#section-4%3A-conversation).
* **Analytics** — how the agent is doing over a time range. See [Section 5: Analytics](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#section-5%3A-analytics).

## Tools

The **Tools** tab has two parts:

* **Tools** and **MCP** — click **Add Tool** to attach your own tools, or connect MCP servers. See [Section 6: Tools](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#section-6%3A-tools).
* **System Tools** — only two are available: [Smart Hang-up](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#smart-hang-up) and [Voicemail Intelligence](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#voicemail-intelligence). The gear icon next to each one opens its settings.

![The Tools tab with the Tools and MCP buttons, the Add Tool button, and the System Tools list with Smart Hang-up and Voicemail Intelligence.](https://mintcdn.com/lechusai/Bm4nSAiwh1gnk2Oe/images/ultra-low-latency-tools.png?fit=max\&auto=format\&n=Bm4nSAiwh1gnk2Oe\&q=85\&s=750b264ae4b029062ab9878c6fa59b48)

Screenshot: the Tools tab. Ultra-low latency agents have two system tools.

> [!NOTE]
>
> **Transfer to agent** and **Transfer to number** aren't in this list. To pass the call to another agent, use a [Squad](https://support.callin.io/Create-AI-Agent/Squads.md).

## Call Action

The **Call Action** tab has four actions:

* **Post-Call Summary Email** — sends the call details to the email addresses you choose when the call ends.
* **Data Sync (Post-Call Webhook)** — sends the call details and captured data to another system, such as a CRM. Enter the webhook URL.
* **Information Capture (Data Extraction)** — click **Add Entity** for each detail the agent should identify and save, like names or dates.
* **Persistence & Connection (Call Retry)** — **Retry Attempts (Retry Count)** sets how many times to try again when the call isn't answered or reaches voicemail, and **Wait Time Between Tries (Retry Delay)** sets the minutes between tries.

![The Call Action tab with the Post-Call Summary Email toggle, the Data Sync webhook field, the Information Capture block with Add Entity, and the Call Retry fields.](https://mintcdn.com/lechusai/Bm4nSAiwh1gnk2Oe/images/ultra-low-latency-call-action.png?fit=max\&auto=format\&n=Bm4nSAiwh1gnk2Oe\&q=85\&s=3b5c6b6a31b4929c7a52ea65a01ae57e)

Screenshot: the Call Action tab of an Ultra-low latency agent.

Each one works as described in [Section 7: Call Action](https://support.callin.io/Create-AI-Agent/Create-Agent-Enchanced.md#section-7%3A-call-action). **Appointment Scheduling**, **Smart Opt-Out**, and **Issue and Complaint Tracking** aren't available in Ultra-low latency agents.

## Goals

The **Goals** tab only exists in Ultra-low latency agents. You list what a good call should achieve. After each call, Callin.io checks whether each goal was met, and it can email you when a call needs attention.

<video autoPlay muted loop playsInline src="https://mintcdn.com/lechusai/Bm4nSAiwh1gnk2Oe/images/ultra-low-latency-goals.mp4?fit=max&auto=format&n=Bm4nSAiwh1gnk2Oe&q=85&s=c57bfa32731f771a4463aa480ea80648" />

Video: add a goal → turn on email alerts → open Advanced options.

### Step 1: What should a good call achieve?

Pick a ready-made goal or write your own:

* **Book an appointment** — the caller agreed to a specific date and time.
* **Qualify the lead** — the call covered the need, the timeline, and whether the caller decides or has budget.
* **Capture an email address** — the agent got a usable email address.
* **Write my own** — your own goal.

Each goal has a **Goal name** and **How do we know it worked?**, where you describe what must happen in the call for the goal to count as met. Use **Add another** to add more goals (up to 20), and the bin icon to remove one.

> [!TIP]
>
> Write each goal as a clear yes/no outcome, like "Book an appointment" or "Get the caller's email". Avoid vague goals like "Be helpful".

### Step 2: Get an email when something's off

Turn on **Email me when a call needs attention** to get one short email per call, only when a goal was missed or took too many retries. Then:

* **Send alerts to** — type an email address and click **Add**. At least one is required (up to 20).
* **Also email me when the caller sounds unhappy** — sends the email even if the goals were met.
* **Advanced options** — **Include hard-to-complete goals** (alerts when a goal succeeded only after many repeats or corrections) and **Include sentiment in the email** (adds the caller's overall mood).

Click **Save** to keep your goals.

## Advanced

The **Advanced** tab has five blocks.

![The Advanced tab with the Background sound toggle, the Record Calls toggle, and the Inbound fallback block with the Fallback number field.](https://mintcdn.com/lechusai/Bm4nSAiwh1gnk2Oe/images/ultra-low-latency-advanced.png?fit=max\&auto=format\&n=Bm4nSAiwh1gnk2Oe\&q=85\&s=efe1d30af416943c7dd9c487f8edb553)

Screenshot: the end of the Advanced tab, with Privacy & Data and Inbound fallback.

* **Voice & Understanding** — **Priority Keywords**: terms the agent should recognize better, separated by commas.
* **Conversation Flow** — **Take turn after silence** (seconds the agent waits after the caller stops speaking), **End conversation after silence** (seconds of silence before the call ends; **-1** means never), and **Max conversation duration** (minutes).
* **Background sound** — **Enable background sound** plays a continuous sound mixed with the agent's voice.
* **Privacy & Data** — **Record Calls** stores the transcript and audio of every call.
* **Inbound fallback** — see below.

### Inbound fallback

**Inbound fallback** is a phone number. If the agent can't answer an incoming call (it's unavailable or the connection fails), the call is forwarded to that number instead of ending. Enter it in **Fallback number**. The number applies to the phone number assigned to the agent.

Leave it empty and the call ends with an error in those cases.

> [!TIP]
>
> For agents that answer incoming calls, add your reception or main office number as the **Fallback number**, so no caller is left without an answer.

## Troubleshooting

### "I can't find the Workflow (or Website widget) tab"

**Cause:** The agent uses the **Ultra-low latency** stack, which doesn't have those tabs.\
**Fix:** Use a **Premium Voice** agent if you need a workflow or a website widget. The stack is chosen when you create the agent.

### "I can't choose the AI model or the call direction"

**Cause:** Ultra-low latency agents don't have the **AI Intelligence (LLM)** or **Call Direction** settings.\
**Fix:** Nothing to fix. The agents list shows these agents as **Inbound & Outbound**. If you need to choose a specific AI model, use a **Premium Voice** agent.

### "How do I set a number for incoming calls when the agent can't answer?"

Use **Inbound fallback** in the **Advanced** tab: enter the **Fallback number**. If you leave it empty, the call ends with an error when the agent can't answer. See [Inbound fallback](#inbound-fallback).

### "I can't add my agent to a squad"

**Cause:** Only Ultra-low latency agents can join a squad.\
**Fix:** Check the agent's stack in the agents list (**Enhanced** label). See [Squads](https://support.callin.io/Create-AI-Agent/Squads.md).


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