Originally published at claudeguide.io/claude-agent-sdk-guide

Claude Agent SDK Guide: Build Automation Agents with Tool Use

The "Claude Agent SDK" is the Anthropic Python/TypeScript SDK combined with the tool use feature — it's not a separate package. An agent is just a loop: send a message, Claude calls a tool, you execute the tool, send the result back, repeat until done in 2026. This guide covers the complete pattern for building reliable production agents.

---

Quick Start

pip install anthropic

import anthropic

client = anthropic.Anthropic()

# Minimal agent with one tool
tools = [{
    "name": "get_weather",
    "description": "Get current weather for a location",
    "input_schema": {
        "type": "object",
        "properties": {
            "location": {"type": "string", "description": "City name"}
        },
        "required": ["location"]
    }
}]

messages = [{"role": "user", "content": "What's the weather in Seoul?"}]

response = client.messages.create(
    model="claude-sonnet-4-5",
    max_tokens=1024,
    tools=tools,
    messages=messages
)

print(response.stop_reason)  # "tool_use" if Claude wants to call a tool

---

The Agentic Loop

The core pattern: run until stop_reason == "end_turn".

python
import anthropic
import json

client = anthropic.Anthropic()

def run_agent(tools: list, tool_executor: callable, initial_message: str) -

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