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

Claude Agent SDK Quickstart: Build Your First Agent in 15 Minutes

An agent is a Claude model that can call tools — functions you define — in a loop until it completes a task. This guide walks from zero to a working agent with two tools (web search and unit converter) in Python or TypeScript in 2026.

Prerequisites: Anthropic API key, Python 3.11+ or Node.js 18+.

What you're building

A research assistant that:

1. Accepts a question
2. Decides whether to search the web or convert a unit
3. Calls the tool
4. Uses the result to answer (or calls another tool)
5. Returns a final answer

---

Python version

Step 1: Install the SDK

pip install anthropic
export ANTHROPIC_API_KEY=sk-ant-your-key-here

Step 2: Define your tools

Tools are Python functions with JSON Schema descriptions. Claude reads the description to decide when to call each tool.

python
import anthropic
import json

client = anthropic.Anthropic()

TOOLS = [
    {
        "name": "web_search",
        "description": "Search the web for current information. Use when the question requires recent facts or data.",
        "input_schema": {
            "type": "object",
            "properties": {
                "query": {"type": "string", "description": "The search query"}
            },
            "required": ["query"]
        }
    },
    {
        "name": "unit_converter",
        "description": "Convert between common units. Supports: km/miles, kg/lbs, celsius/fahrenheit, usd/krw.",
        "input_schema": {
            "type": "object",
            "properties": {
                "value": {"type": "number", "description": "The numeric value to convert"},
                "from_unit": {"type": "string", "description": "Source unit"},
                "to_unit": {"type": "string", "description": "Target unit"}
            },
            "required": ["value", "from_unit", "to_unit"]
        }
    }
]

def web_search(query: str) -

Complete, runnable Python and TypeScript code throughout.

[→ Get Agent SDK Cookbook — $49](https://shoutfirst.gumroad.com/l/ogxhmy?utm_source=claudeguide&utm_medium=article&utm_campaign=claude-agent-sdk-quickstart)

*30-day money-back guarantee. Instant download.*