Function Calling & Tool Use

Give your AI models superpowers by connecting them to external functions, APIs, and databases. Learn function calling across OpenAI, Anthropic, and Google, and build production-ready tool-using AI agents.

Start Course → Build Tools
6
Lessons
45+
Examples
~2.5hr
Total Time
⚡
Practical

What You'll Learn

By the end of this course, you'll be able to define tools, handle function calls, and build AI agents that interact with external systems across all major providers.

🔧

Tool Definitions

Define function schemas that tell the model what tools are available, what parameters they accept, and when to use them.

🔁

Multi-Provider Support

Implement function calling across OpenAI, Anthropic Claude, and Google Gemini with provider-specific patterns and best practices.

⚙

Execution Loops

Build robust tool execution loops that handle multiple function calls, errors, retries, and parallel tool use.

💡

Production Patterns

Learn security considerations, validation, error handling, and architectural patterns for production tool-using systems.

Course Lessons

Follow the lessons in order for a complete understanding, or jump to any topic.

Beginner

1. Introduction

What is function calling? How AI models decide to use tools, the request-response cycle, and why tool use is transformative for AI applications.

10 min read →
 Intermediate

2. OpenAI Functions

Implement function calling with GPT-4o: tool definitions, handling tool_calls, parallel function calling, and the tool choice parameter.

15 min read →
 Intermediate

3. Anthropic Tools

Claude's tool use API: defining tools, handling tool_use content blocks, tool_result messages, and multi-step tool chains.

15 min read →
 Intermediate

4. Google Functions

Function calling with Gemini: function declarations, automatic function calling mode, and Google's function calling configuration.

12 min read →
 Advanced

5. Building Tools

Design and build production-ready tools: API wrappers, database queries, file operations, and composing tools into agent workflows.

15 min read →
 Advanced

6. Best Practices

Security, validation, error handling, rate limiting, testing strategies, and production deployment patterns for tool-using AI systems.

12 min read →

Prerequisites

What you need before starting this course.

Before You Begin:
  • Experience with at least one AI API (OpenAI, Anthropic, or Google)
  • Familiarity with JSON Schema (for defining function parameters)
  • Python or JavaScript proficiency for code examples