Function Calling & Tool Use: Complete Guide for Prompt Engineers

Define tools the model can call to take structured actions — web search, database queries, API calls, code execution. Learn when to use it, see a real example, and understand the best practices.

When to Use This Technique

AI agents, workflow automation, or any use case requiring the model to interact with external systems.

Example Prompt

Define: {name: 'search_web', description: 'Search for current information', parameters: {query: string}}. Model decides when to call this tool.

Pro Tips

✓Write detailed tool descriptions — the model reads these
✓Keep tool names and parameter names semantic
✓Handle tool errors gracefully in your prompt
✓Test that the model uses tools when it should AND when it shouldn't

More Practice Prompts

Define: {name: 'search_web', description: 'Search for current information', parameters: {query: string}}. Model decides when to call this tool.

FAQ

When should I use Function Calling & Tool Use?

AI agents, workflow automation, or any use case requiring the model to interact with external systems.

What difficulty level is Function Calling & Tool Use?

Function Calling & Tool Use is considered Advanced level in the Agent Patterns category.

Quick Facts

DifficultyAdvanced

CategoryAgent Patterns