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

# Agents

> An agent is the instructions, voice and settings behind your phone line.

An agent answers and makes calls for your business. In the API it is called an assistant.

## Versions

An agent has versions. A version is the full set of settings: the greeting, the instructions, the language, the models and voice, and what happens after the call.

* You edit a **draft** version.
* **Publish** a version to make it live. A published version is immutable.
* To change a live agent, create a new draft, test it, then publish it.

Numbers and campaigns use the published version. Browser test calls can use the latest draft instead, so you can try a change before it reaches callers.

## What a version contains

| Setting | What it does |
| - | - |
| `greeting_text` | The first thing the agent says. |
| `system_prompt` | The instructions: who the agent is, what it should do and what it should avoid. |
| `language` | The language of the call. |
| `mode` | `cascade` or `s2s`. See below. |
| `knowledge_base_ids` | Knowledge bases the agent can search during a call. See [Knowledge](https://docs.larynth.com/concepts/knowledge.md). |
| `tools` | Actions the agent can take: end the call, record an opt-out, call an HTTP endpoint, or transfer. See [Handoff](https://docs.larynth.com/concepts/handoff.md). |
| `post_call` | The summary, the fields to extract and a success check. See [Summaries and extraction](https://docs.larynth.com/concepts/summaries.md). |
| `max_call_seconds` | A cap on call length. |

Voices and models are chosen from the catalog. List what is enabled with `GET /v1/catalog/voices` and `GET /v1/catalog/models`.

## Modes

* **Cascade** uses a separate speech-to-text model, language model and voice. You pick each one.
* **S2S** (speech to speech) uses one model that listens and speaks.

Both modes cost the same per minute. See [Billing](https://docs.larynth.com/concepts/billing.md).

## Write good instructions

* Say who the agent answers for and what the business does.
* List the few things callers usually want, and what to do for each.
* Say what to collect (name, number, reason) and what to do with it.
* Say when to hand the call to a person.
* Say what the agent should not do, such as quoting prices you have not given it.

Keep the greeting short. Then test with real questions in the [browser](https://docs.larynth.com/guides/test-in-browser.md).

## Outbound calls

An agent that places calls should be briefed for that: who it is calling for, why, and how to end politely if the person is not interested. Outbound calls also go through compliance checks before they dial. See [Compliance](https://docs.larynth.com/concepts/compliance.md).


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