What is tool use in Claude API

import os
import anthropic

client = anthropic.Anthropic(api_key=os.environ["ANTHROPIC_API_KEY"])

# Define a simple tool that Claude can call
tools = [
    {
        "name": "get_current_time",
        "description": "Returns the current UTC time as a string.",
        "parameters": {}
    }
]

# Simulate a tool execution function

def execute_tool(tool_name):
    from datetime import datetime
    if tool_name == "get_current_time":
        return datetime.utcnow().isoformat() + "Z"
    return "Tool not found"

# Example conversation where Claude uses the tool
messages = [
    {"role": "user", "content": "What time is it now?"}
]

# Create a chat completion with tool use enabled
response = client.messages.create(
    model="claude-3-5-sonnet-20241022",
    system="You can call external tools to answer user queries.",
    messages=messages,
    tools=tools,
    max_tokens=200
)

# Check if Claude requested a tool call
if response.tool_calls:
    tool_call = response.tool_calls[0]
    tool_result = execute_tool(tool_call["name"])
    # Send tool result back to Claude
    followup = client.messages.create(
        model="claude-3-5-sonnet-20241022",
        system="You can call external tools to answer user queries.",
        messages=messages + [{"role": "tool", "name": tool_call["name"], "content": tool_result}],
        max_tokens=200
    )
    print(followup.content[0].text)
else:
    print(response.content[0].text)