Building the Tool Socket

Claude interacts with your code via Tools (Function Calling). These are defined using standard JSON Schema. Precise descriptions in the input_schema are critical; they aren't just for developers-the model uses these descriptions as 'instructions' to understand when and how to call the tool.

The tool_choice Parameter

By default (auto), Claude decides when to use a tool. For deterministic pipelines, you can override this logic:

• auto: Model decides probabilistic selection.
• any: Forces Claude to use at least one tool from your list.
• tool: Forces Claude to use a specific tool ID immediately.

// Forcing a specific tool
"tool_choice": {"type": "tool", "name": "get_weather"}