Function Calling Overview

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Introduction

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Common Use Cases

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Call Management

• Transfer calls: Route to human agents or other departments
• End calls: Gracefully terminate conversations
• Send DTMF tones: Navigate phone menus

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Business Operations

• Book appointments: Integrate with scheduling systems
• Check availability: Query calendars or inventory
• Process orders: Create, modify, or cancel orders

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Data Integration

• Retrieve information: Pull data from CRMs, databases, or APIs
• Update records: Modify customer information or case details
• Send notifications: Trigger emails, SMS, or push notifications

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How Function Calling Works

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The Process

1. Agent Decision: Based on the conversation context, the LLM determines when a function is needed
2. Parameter Extraction: The agent extracts required information from the conversation
3. Function Execution: Retell calls your function with the extracted parameters
4. Response Handling: The function result is processed and incorporated into the conversation

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Technical Overview

{
  "function": "book_appointment",
  "arguments": {
    "date": "2024-03-15",
    "time": "14:00",
    "customer_name": "John Smith"
  }
}

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Additional Resources

• OpenAI’s Function Calling Guide: Technical deep dive
• Function Calling Tutorial: Step-by-step implementation guide

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Configuring Tool Calls

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Dashboard Configuration

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Available Function Types

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1. Pre-built Functions

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2. Custom Functions

• Integrate with your APIs: Connect to CRM, ERP, or custom systems
• Execute business logic: Validate data, calculate prices, check inventory
• Trigger workflows: Start processes in other systems

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Custom Function Features

• Flexible parameters: Define any input structure
• Async execution: Run in background without blocking conversation
• Error handling: Graceful fallbacks for failures
• Response control: Customize what the agent says during/after execution

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3. Code Tool

• Data transformation: Format, combine, or compute values from dynamic variables
• Simple API calls: Fetch data using the built-in fetch() function
• Logic and calculations: Implement conditional logic, math, or string operations

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Video Tutorial

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Additional Resources

• Community Templates: Real-world function examples
• API Reference: Technical documentation
• Best Practices: Writing effective function prompts