Tool Use & Function Calling
What is the difference between tool_choice auto and any?
QUICK ANSWER
tool_choice 'auto' allows Claude to choose whether to write a text response or execute a tool, whereas 'any' forces Claude to call at least one tool before responding.
Options Comparison
- auto: Best for standard user chat. The assistant will answer questions using text, and only call tools when external database information is requested.
- any: Best for automated agents. Ensures the output starts a tool action, preventing the model from writing conversational chat.
Verified against: Anthropic Tool Choice Spec