What is 'tool use' (also called function calling) in the context of Claude?
Select an answer to reveal the explanation.
Short Explanation and Infographic
Tool use is like Claude raising its hand and saying 'I need to look that up' — it signals which tool to call and with what arguments, the developer runs it, then feeds the result back to Claude.
Full explanation below image
Full Explanation
Tool use allows developers to define functions (tools) that Claude can call during a conversation. Claude signals its intent to use a tool by returning a structured 'tool_use' content block with the tool name and arguments. The developer's application then executes the actual function and returns the result to Claude, which incorporates it into its final response. This enables Claude to access real-time data, call APIs, run computations, etc. Option A is a literal misinterpretation. Option C describes autonomous code execution, which is a different (and more complex) capability. Option D describes compilation, completely unrelated.