Tool Use in Claude: Official Course · Lesson 1
Tool Use Overview
What function calling is, why you'd extend Claude with tools, and how the 4-step tool use cycle works end to end.
Practical exercise
What to do after this lesson
Sketch the 4-step tool use cycle for a pizza ordering chatbot with a check_menu tool. Describe each step in words, including what data flows in each direction.
Task grader
Sketch the 4-step tool use cycle for a pizza ordering chatbot with a check_menu tool. Describe each step in words, including what data flows in each direction.
Ready-to-use prompt
Template for this lesson
Copy and adapt to your context. Text in angle brackets should be replaced.
I'm building a Claude agent with tools. Business scenario: <describe the task> What tools do I need? For each tool, suggest: 1. Name and description 2. Input parameters (JSON Schema) 3. What the function should return 4. When Claude should call it
Prompt sandbox
Common mistakes
What people get wrong
- Thinking Claude executes code itself — it only requests a call.
- Forgetting to return tool_result — Claude is waiting and can't continue.
- Writing weak tool descriptions — Claude decides which tool to call based on description.