Tool use is what transforms chatbots into agents. The ability to call functions, interact with APIs, execute code, and manipulate external systems enables agents to take real actions in the world. This guide covers function calling capabilities in detail.

Function Calling Flow

How Agents Use Tools

User: "What's the weather in Tokyo?"

Agent decides to call weather_api tool

Extracts parameters: {city: "Tokyo"}

Executes API call, gets result

Formats response: "Tokyo is 22°C and sunny"

Tool Definition

{
  "name": "get_weather",
  "description": "Get current weather for a city",
  "parameters": {
    "type": "object",
    "properties": {
      "city": {
        "type": "string",
        "description": "City name"
      },
      "units": {
        "type": "string",
        "enum": ["celsius", "fahrenheit"],
        "default": "celsius"
      }
    },
    "required": ["city"]
  }
}

Parameter Extraction

Agents extract structured parameters from natural language:

"Send $50 to john@example.com for the pizza"

↓ Extracted parameters ↓

{
  "function": "send_payment",
  "amount": 50,
  "recipient": "john@example.com",
  "note": "pizza"
}

Tool Selection

When multiple tools available, agents choose the right one:

Query: "What's my account balance?"

Available tools:

• get_account_balance ✅ SELECTED
• get_transaction_history
• transfer_money

Multi-Tool Execution

Agents can chain multiple tool calls:

User: "Email me a summary of my top 5 expenses this month"

→ Agent executes:

1. get_transactions(start_date, end_date)

2. analyze_expenses(transactions)

3. generate_summary(top_5_expenses)

4. send_email(user.email, summary)

Error Handling

When Tools Fail

• Retry with adjusted parameters
• Try alternative tool
• Explain issue to user
• Suggest manual alternative

Conclusion

Tool use capabilities are what make agents truly useful. By mastering function calling, parameter extraction, and multi-tool orchestration, you create agents that can take meaningful actions beyond just generating text.

Tool Use and Function Calling Capabilities in AI Agents

Function Calling Flow

How Agents Use Tools

Tool Definition

Parameter Extraction

Tool Selection

Multi-Tool Execution

Error Handling

When Tools Fail

Conclusion

Equip your agents with tools

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