Designing Simple Tool Interfaces › Looking Ahead

You now understand how to design tool interfaces that agents can use effectively. We've covered:

• The three components of a tool: the function, the description, and the registry
• The six-step workflow for tool use
• Key design principles for creating agent-friendly tools
• How agents choose between multiple tools
• When to use tools and when not to

In the next chapter, we'll take these concepts and build something concrete: we'll add a calculator tool to our personal assistant. You'll see exactly how to implement tool use from scratch, step by step, creating an agent that can perform precise calculations instead of guessing at math problems.

The framework we've designed here is intentionally simple and library-agnostic. Real-world frameworks like LangChain, LlamaIndex, or Anthropic's SDK provide more sophisticated tool handling, but they all follow these same fundamental principles. Understanding the basics gives you the foundation to use any framework effectively.