Tools — Giving Your Agent Superpowers

# BAD: vague, Claude won't know when to use this
{"name": "search", "description": "Search for things"}

# GOOD: specific, tells Claude exactly when and how to use it
{ "name": "web_search", "description": ( "Search the web for current information about a topic. " "Use this when you need facts, recent events, or data you don't know. " "Returns a list of relevant snippets with URLs." )
}

import anthropic, json, sqlite3, os, urllib.request
from pathlib import Path

client = anthropic.Anthropic()

# ── Setup: create a sample SQLite database ─────────
def setup_demo_db(): conn = sqlite3.connect("demo.db") conn.execute(""" CREATE TABLE IF NOT EXISTS sales ( id INTEGER PRIMARY KEY, product TEXT, revenue REAL, month TEXT, region TEXT ) """) conn.execute("DELETE FROM sales") conn.executemany( "INSERT INTO sales VALUES (?,?,?,?,?)", [ (1, "Widget A", 45000, "2024-01", "West"), (2, "Widget B", 32000, "2024-01", "East"), (3, "Widget A", 67000, "2024-02", "West"), (4, "Widget C", 89000, "2024-02", "North"), (5, "Widget B", 54000, "2024-03", "East"), ] ) conn.commit(); conn.close()

# ── Tool implementations ───────────────────────────
def web_search(query: str) -> str: # Using DuckDuckGo Instant Answer API (no key required) url = f"https://api.duckduckgo.com/?q={urllib.parse.quote(query)}&format=json&no_html=1" try: import urllib.parse with urllib.request.urlopen(url, timeout=5) as resp: data = json.loads(resp.read()) abstract = data.get("AbstractText", "") if abstract: return abstract[:500] return f"No instant answer found for '{query}'. Try a more specific query." except Exception as e: return f"Search error: {e}"

def read_file(path: str) -> str: try: p = Path(path) if not p.exists(): return f"File not found: {path}" content = p.read_text() if len(content) > 4000: content = content[:4000] + "\n[truncated]" return content except Exception as e: return f"Read error: {e}"

def http_get(url: str) -> str: try: with urllib.request.urlopen(url, timeout=8) as resp: body = resp.read().decode() return body[:2000]  # truncate large responses except Exception as e: return f"HTTP error: {e}"

def query_db(sql: str) -> str: try: # Only allow SELECT for safety if not sql.strip().upper().startswith("SELECT"): return "Only SELECT queries are allowed." conn = sqlite3.connect("demo.db") conn.row_factory = sqlite3.Row rows = conn.execute(sql).fetchall() conn.close() if not rows: return "Query returned no rows." result = [dict(r) for r in rows] return json.dumps(result, indent=2) except Exception as e: return f"DB error: {e}"

def save_note(title: str, content: str) -> str: fname = f"notes/{title.replace(' ','-')}.txt" os.makedirs("notes", exist_ok=True) Path(fname).write_text(content) return f"Saved to {fname}"

# ── Tool definitions ───────────────────────────────
TOOLS = [ {"name":"web_search","description":"Search the web for current facts. Use when you need information you don't have. Returns a text snippet.", "input_schema":{"type":"object","properties":{"query":{"type":"string"}},"required":["query"]}}, {"name":"read_file","description":"Read a local file. Use to access local documents, configs, or data files.", "input_schema":{"type":"object","properties":{"path":{"type":"string"}},"required":["path"]}}, {"name":"http_get","description":"Make an HTTP GET request to a URL. Use for REST APIs or fetching web content.", "input_schema":{"type":"object","properties":{"url":{"type":"string"}},"required":["url"]}}, {"name":"query_db","description":"Run a SQL SELECT query on the sales database. Tables: sales(id,product,revenue,month,region).", "input_schema":{"type":"object","properties":{"sql":{"type":"string"}},"required":["sql"]}}, {"name":"save_note","description":"Save information to a file for later. Use to record findings or summaries.", "input_schema":{"type":"object","properties":{"title":{"type":"string"},"content":{"type":"string"}},"required":["title","content"]}},
]

def execute_tool(name, inp): return { "web_search": lambda: web_search(inp["query"]), "read_file":  lambda: read_file(inp["path"]), "http_get": lambda: http_get(inp["url"]), "query_db": lambda: query_db(inp["sql"]), "save_note":  lambda: save_note(inp["title"], inp["content"]), }[name]()

# Same agent loop as Day 1 (reusable)
def run_agent(task, max_steps=15): messages = [{"role":"user","content":task}] for step in range(max_steps): resp = client.messages.create( model="claude-sonnet-4-5", max_tokens=2048, tools=TOOLS, messages=messages ) if resp.stop_reason == "end_turn": return resp.content[0].text results = [] for b in resp.content: if b.type == "tool_use": print(f"  [{step+1}] {b.name}({list(b.input.keys())})") result = execute_tool(b.name, b.input) results.append({"type":"tool_result","tool_use_id":b.id,"content":str(result)}) messages += [{"role":"assistant","content":resp.content},{"role":"user","content":results}] return "Max steps reached."

if __name__ == "__main__": setup_demo_db() result = run_agent(""" Analyze our sales data: 1. Query total revenue by product 2. Find the best-performing region 3. Save a summary note titled 'Sales Analysis Q1 2024' Be specific with numbers. """) print("\n=== Final Answer ===\n", result)