Tool Use & Function Calling

Defining tools in the Claude API — the schema, how Claude decides when to call tools, and result handling.

What You Will Learn

• Tool definition schema: name, description, input_schema
• How Claude decides whether to call a tool vs answer directly
• Sending tool results back to Claude for the next step
• Parallel tool calls: when Claude calls multiple tools at once
• Error handling: what to do when a tool call fails