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.
tools	Actions the agent can take: end the call, record an opt-out, call an HTTP endpoint, or transfer. See Handoff.
post_call	The summary, the fields to extract and a success check. See Summaries and extraction.
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.

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.

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.