Designing Simple Tool Interfaces › When Not to Use a Tool
Michael BrenndoerferJune 25, 20252 min read
AI Agent HandbookAll chapters Part 5 of 15Tool Use - Extending the Agent's Abilities
Designing Simple Tool Interfaces › When Not to Use a ToolOne section · Sections in this chapter9 / 12 ↓
Sections in this chapter12
An important part of tool design is knowing when the agent shouldn't use a tool. Not every question requires external information:
User: What's the capital of France?The agent can answer this from its general knowledge. It doesn't need to search the web or call an API. Using a tool here would be slower and waste resources.
Good tool use involves:
- Using tools when needed: For current information, precise calculations, or actions
- Not using tools when not needed: For general knowledge questions the agent can answer directly
- Failing gracefully: If a tool isn't available or returns an error, the agent should explain the limitation
You can guide this behavior through your system prompt:
In[10]:
Codesystem_prompt = """
You are a helpful assistant with access to tools.
Use tools when you need:
- Current, real-time information (weather, news, stock prices)
- Precise calculations
- To take actions (send emails, update records)
Do NOT use tools for:
- General knowledge questions you can answer directly
- Simple arithmetic you can handle reliably
- Questions about your own capabilities
If you're unsure whether to use a tool, prefer using it to ensure accuracy.
"""