What Is Tool Use?
Claude can process text and images, and since March 2025 can search the web. With tool use (also called function calling), Claude can do even more — query databases, call APIs, run code, and interact with any system you connect. You define the tools, and Claude decides when and how to use them.
Think of tools as giving Claude hands to go with its brain.
Build a Tool Definition
Define a tool that Claude can use. Fill in the fields below to see the JSON schema update in real-time.