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

# Single Prompt Agent Overview

> Simple, fast, and effective for straightforward conversational scenarios

## What is a Single Prompt Agent?

A single prompt agent uses one comprehensive prompt (called a "preamble") to define all agent behaviors. This approach is the simplest and fastest way to create a voice agent, perfect for straightforward conversational scenarios.

## When to Use Single Prompt Agents

Single prompt agents are ideal when:

* Your conversation flow is relatively linear
* You don't need complex conditional branching
* Your prompt is under 500 words
* You're using 3 or fewer custom tools/functions
* You need to build and deploy quickly

## When to Upgrade to Flow Agent

Consider upgrading to a Flow Agent when:

* Your single prompt exceeds 500 words
* You need complex decision trees with multiple paths
* You require more than 3 custom tools
* You need fine-grained control over different conversation stages
* You want visual representation of your conversation flow
* You need to reuse conversation components across agents

## Key Components

### 1. **Preamble (System Prompt)**

The core instructions that define your agent's behavior, personality, task, and guidelines. This is where you tell the agent:

* Who it is (identity)
* How to behave (style and tone)
* What to do (tasks and goals)
* What not to do (guardrails and limitations)

### 2. **Greeting Message**

The first thing your agent says when a call starts. Can be:

* **Static**: A fixed greeting message
* **Prompt-based**: Dynamically generated based on context

### 3. **Global Settings**

Configuration applied to all conversations:

* Voice and language selection
* LLM model and parameters
* Response timing and interruption handling
* Call behavior settings

### 4. **Knowledge Base** (Optional)

Upload documents, web content, or custom text that your agent can reference during conversations.

### 5. **Tools** (Optional)

Extend your agent's capabilities with tools:

* **API Request Tools** — server-side API calls (work on phone and web)
* **MCP Tools** — Model Context Protocol integrations (server-side)
* **Webhook Tools** — trigger external webhooks during conversation
* **Web Tools** — client-side JavaScript functions that run in the browser (SDK deployments only). These can navigate the user, open modals, read page data, and more. See [Web Tools](/agents/tools/web-tools) for details.

### 6. **Variables & Parameters** (Optional)

Define structured data that your agent should collect during calls, with optional outcome schema for structured responses. Single-prompt agents support **system variables** and **custom variables** (passed as `params`). See [Variable System](/agents/variables/introduction) for full reference.

## Setup Process

Creating a single prompt agent follows three main steps:

### Step 1: Write the Prompt

* Define agent identity and personality
* Set style guardrails and conversation tone
* Specify response guidelines
* Outline tasks and procedures

**[→ Learn More: Writing a Single Prompt](./write-prompt)**

### Step 2: Configure Basic Settings

* Select voice and language
* Configure call behavior (interruptions, delays, timeouts)
* Set up noise cancellation and audio processing
* Enable advanced features (gender detection, smart call end, etc.)

**[→ Learn More: Configure Basic Settings](./configure-settings)**

### Step 3: Add Integrations (Optional)

* Connect knowledge bases
* Add custom tools and functions
* Configure webhooks
* Define outcome parameters

**[→ Learn More: Knowledge Base](/agents/knowledge-base/introduction)**
**[→ Learn More: Tools & Functions](/agents/tools/introduction)**
**[→ Learn More: Webhooks](/agents/webhooks/introduction)**

## Example Use Cases

### Customer Support Bot

Simple Q\&A agent that answers common questions using knowledge base:

* **Preamble**: \~200 words defining personality and guidelines
* **Knowledge Base**: FAQ documents and help articles
* **Tools**: None or minimal (ticket creation)

### Appointment Scheduler

Collects information and books appointments:

* **Preamble**: \~300 words with booking procedure
* **Tools**: Calendar availability check, booking function
* **Variables**: Name, phone, date, time, service type

### Lead Qualification

Gathers lead information and routes to sales:

* **Preamble**: \~250 words with qualification questions
* **Variables**: Company size, budget, timeline, needs
* **Outcome**: Structured lead data

## Key Features

### Flexible Greeting

Choose between static greetings for consistency or dynamic greetings that adapt to context (time of day, caller information, etc.).

### Advanced Call Settings

* **Response Delay**: Control how quickly the agent responds (100-1500ms)
* **Interruption Handling**: Allow or prevent user interruptions
* **Inactivity Timeout**: Automatically handle silent callers (5–60 seconds)
* **Max Call Duration**: Set maximum call length (30 seconds – 1 hour)

### Audio Processing

* **Noise Cancellation**: Remove background noise (disabled, telephony optimized, or general use cases)
* **Background Noise**: Add ambient sound for realism
* **Thinking Voice**: Add natural pauses and filler words

### Intelligence Features

* **Gender Detection**: Detect caller gender for personalized responses
* **Smart Call End**: Automatically end calls when conversation concludes
* **Language Dialect Switcher**: Adapt to caller's dialect
* **Speaker Identification**: Identify different speakers on the same call
* **Agentic RAG**: Advanced knowledge retrieval with reasoning

## Benefits

### ✅ Quick to Build

Get started in minutes with a single comprehensive prompt.

### ✅ Easy to Maintain

All agent behavior defined in one place makes updates simple.

### ✅ Cost-Effective

Simpler architecture means lower latency and potentially lower costs.

### ✅ Perfect for MVPs

Fastest path from idea to working agent.

## Limitations

### ⚠️ Limited Complexity

Not suitable for highly branching conversation flows.

### ⚠️ Prompt Size Constraints

Large prompts (>500 words) become harder to manage and may reduce performance.

### ⚠️ Less Control

Cannot fine-tune behavior for specific conversation stages independently.

### ⚠️ Tool Limitations

Best with 3 or fewer tools; more tools can confuse the agent.

## Template Structure

Here's a recommended prompt structure:

```
## Identity
[Define who the agent is and what it represents]

## Style Guardrails
[Set tone, personality, and conversation style]

## Response Guidelines
[Specify how to format responses and handle edge cases]

## Task & Goals
[Outline what the agent should accomplish]

## Objection Handling
[Provide guidance for common objections or difficult scenarios]
```

**[→ See Full Template & Examples](./write-prompt)**

## Next Steps

Ready to create your first single prompt agent?

1. **[Write Your First Prompt](./write-prompt)** - Learn prompt engineering best practices
2. **[Configure Settings](./configure-settings)** - Set up voice, timing, and behavior
3. **[Add Knowledge Base](/agents/knowledge-base/introduction)** - Enhance with company information
4. **[Test Your Agent](/agents/testing/introduction)** - Test in browser or via phone call

***

**Need more power?** Check out **[Flow Agent Overview](../flow-agent/overview)** for complex conversation flows.