Agent Builder
Understand the three conversation modes and configuration options in the BusyBots voice agent builder.
The agent builder is where you design how a voice agent behaves — from a single system prompt to a fully visual conversation flow.
Conversation modes
Every agent runs in one of three modes, set when you create it:
Single Prompt
One system prompt drives the entire conversation. The LLM handles branching naturally based on your instructions. This is the fastest way to get an agent live and works well for straightforward use cases (FAQ answering, appointment booking, lead qualification).
Multi-State
Define distinct states the conversation moves through (e.g., greeting → qualify → collect details → confirm), each with its own instructions and transition rules. Useful when you want explicit control over conversation phases without building a full visual flow.
Conversation Flow
A visual, node-based flow builder for complex call logic — branching paths, conditions, tool calls, and transfers, all connected as a flow diagram. Best for agents with many possible paths (e.g., multi-department call routing).
You can switch an agent's mode later, but each mode stores its configuration independently — switching modes means reconfiguring the conversation logic in the new mode.
Core configuration
Regardless of mode, every agent has:
| Setting | Description |
|---|---|
| Name & description | Internal labels, shown in the dashboard |
| Voice | Selected from the voice library — filtered by supported language |
| Language | Primary language for STT/TTS; 20+ languages supported |
| LLM | The underlying model powering the agent's reasoning |
| Status | draft while configuring, published when live |
Choosing an LLM
Retell supports a wide range of LLMs. Faster, cheaper models are a good default for simple conversations; if you need stronger reasoning for complex flows, choose a more capable model. You can change the LLM at any time without rebuilding the conversation logic.
Tool access
Voice agents can be configured with tools that give them CRM data access during a call — for example, looking up a contact or checking an appointment. These are delivered as HTTP webhooks under the hood (Retell Custom Functions) so the agent can speak real data back to the caller. CRM tool access for user-created agents is an active area of build-out — check your agent's tool configuration for what's currently available.
Testing changes
Use the test call feature in the agent detail view after any change — it places a live call against your current (unpublished or published) configuration so you can verify behavior before customers hear it.