Tool functions

Overview

• Tools allow Claude to retrieve extra information by executing Python functions automatically
• The notebook "001 Tools" contains boilerplate code and helper functions to save time
• Focus on implementing tools without helper functions initially to avoid confusion during refactoring

Tool Function Best Practices

Naming and Arguments

• Use well-named and descriptive function arguments
• Argument names should hint at their purpose

Input Validation

• Always validate inputs and raise errors if something is wrong
• Validation prevents Claude from receiving invalid data

Error Messages

• Include meaningful error messages when raising errors
• Claude can see error messages and may retry the tool call with corrected parameters
• Error messages guide Claude toward fixing mistakes (e. g. , "location cannot be empty")

Example: get_current_date_time Function

Structure

• Takes a date_format parameter with a default value (e. g. , "%Y-%m-%d %H:%M:%S")
• Returns the current date and time formatted according to the provided format string
• Uses datetime. now(). strftime(date_format) to format output

Validation

• Check that date_format is not an empty string
• Raise ValueError with message "date format cannot be empty" if validation fails
• Prevents Claude from passing invalid format strings

Usage Examples

• Default format returns: year-month-day hour:minute:second
• Custom format (e. g. , "%H:%M") returns only hour and minute

Takeaways

• Tools allow Claude to automatically execute Python functions to retrieve extra information
• Always validate tool function inputs and raise meaningful errors so Claude can see what went wrong and retry with corrected parameters
• Use well-named, descriptive function arguments and include helpful error messages that guide Claude toward fixing mistakes
• Tool functions should have clear structure with default parameter values and proper error handling (e. g. , checking for empty strings)