#9 Tool-Using Agent — Flask + Claude ReAct loop (private validation build)

.env.example

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+# Claude API key — required (the whole app is a function-calling / tool-use loop).
+ANTHROPIC_API_KEY=sk-ant-...
+ANTHROPIC_MODEL=claude-haiku-4-5
+# The tools themselves (weather, Wikipedia) are keyless — no other secrets needed.

.gitignore

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+__pycache__/
+*.pyc
+.env
+.venv/
+venv/
+*.log

Dockerfile

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+# Tool-Using Agent — runs on Hugging Face Spaces, Render, Railway, Fly.io, etc.
+FROM python:3.11-slim
+WORKDIR /app
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+COPY . .
+ENV PORT=7860
+EXPOSE 7860
+CMD ["python", "app.py"]

README.md

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 ---
-title: Tool Using Agent
-emoji: 🚀
-colorFrom: yellow
-colorTo: red
+title: Tool-Using Agent
+emoji: 🛠️
+colorFrom: indigo
+colorTo: purple
 sdk: docker
+app_port: 7860
 pinned: false
+short_description: An AI agent that calls live tools (ReAct) · 30-in-15 #9
 ---
 
-Check out the configuration reference at https://huggingface.co/docs/hub/spaces-config-reference
+# Tool-Using Agent 🛠️
+
+Ask a question and watch the AI **call real, live tools** to answer it — a calculator, the current
+date/time, live **weather**, and **Wikipedia** — running the **ReAct** loop (decide → call a tool →
+read the result → repeat) and showing every tool call it made.
+
+> Project **#9** of my *"30 AI Projects in 15 Days"* build-in-public challenge.
+
+**▶ Live demo: https://agent.gritai.solutions**
+
+![demo](demo.png)
+
+## Try
+- *"What's a 15% tip on $47.80, and what's the weather in Paris?"* → calculator + weather
+- *"Who invented the World Wide Web, and how many days ago was Jan 1 2000?"* → Wikipedia + date + calc
+
+## How it works
+- The model is given four **keyless** tools (Open-Meteo for weather, MediaWiki for Wikipedia, plus a
+  safe calculator and a clock). It decides which to call — possibly several — and the server executes
+  them and feeds results back, looping until the model can answer (capped at a few steps).
+- **Transparency:** the UI shows the exact tool calls and their live results, so you can see the
+  reasoning, not just the answer.
+- The calculator is a **safe AST evaluator** (no `eval`), limited to arithmetic + a few math functions.
+
+## Run locally
+```bash
+pip install -r requirements.txt
+export ANTHROPIC_API_KEY=sk-ant-...
+python app.py                            # http://127.0.0.1:7860
+```
+
+## Deploy (always-on)
+Ships with a `Dockerfile` — works on **Hugging Face Spaces**, Render, Railway, or Fly.io.
+Set `ANTHROPIC_API_KEY` as a secret. The tools need no other keys.
+
+---
+Built by **Robert Lucyk** · [GritAI Solutions](https://gritai.solutions) · part of the 30-in-15 challenge.

app.py

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+#!/usr/bin/env python
+"""Tool-Using Agent — ask a question and watch the AI call real, live tools to answer it:
+a calculator, the current date/time, live weather, and Wikipedia. It runs the ReAct loop
+(decide → call tool → read result → repeat) and shows every tool call it made.
+
+All tools are keyless (Open-Meteo + MediaWiki), so the only secret is ANTHROPIC_API_KEY.
+
+  pip install flask requests anthropic
+  python app.py            # http://127.0.0.1:7860
+
+Project #9 of the "30 Projects in 15 Days" challenge — GritAI.
+"""
+import os, ast, json, math, operator, datetime, urllib.parse
+from flask import Flask, request, jsonify, Response
+import requests
+
+PORT = int(os.environ.get("PORT", "7860"))
+ANTHROPIC_KEY = os.environ.get("ANTHROPIC_API_KEY")
+ANTHROPIC_MODEL = os.environ.get("ANTHROPIC_MODEL", "claude-haiku-4-5")
+MAX_STEPS = 6
+UA = {"User-Agent": "GritAI-ToolAgent/1.0 (https://gritai.solutions)"}
+
+# --------------------------------------------------------------------------- tools
+_OPS = {ast.Add: operator.add, ast.Sub: operator.sub, ast.Mult: operator.mul,
+        ast.Div: operator.truediv, ast.Pow: operator.pow, ast.Mod: operator.mod,
+        ast.FloorDiv: operator.floordiv, ast.USub: operator.neg, ast.UAdd: operator.pos}
+_FUNCS = {"sqrt": math.sqrt, "abs": abs, "round": round, "log": math.log, "log10": math.log10,
+          "sin": math.sin, "cos": math.cos, "tan": math.tan, "pi": math.pi, "e": math.e,
+          "floor": math.floor, "ceil": math.ceil, "exp": math.exp, "min": min, "max": max}
+
+
+def _safe_eval(node):
+    if isinstance(node, ast.Constant):
+        if isinstance(node.value, (int, float)):
+            return node.value
+        raise ValueError("only numbers")
+    if isinstance(node, ast.BinOp):
+        return _OPS[type(node.op)](_safe_eval(node.left), _safe_eval(node.right))
+    if isinstance(node, ast.UnaryOp):
+        return _OPS[type(node.op)](_safe_eval(node.operand))
+    if isinstance(node, ast.Name):
+        if node.id in _FUNCS:
+            return _FUNCS[node.id]
+        raise ValueError(f"unknown name {node.id}")
+    if isinstance(node, ast.Call):
+        fn = _FUNCS.get(getattr(node.func, "id", ""))
+        if not callable(fn):
+            raise ValueError("unknown function")
+        return fn(*[_safe_eval(a) for a in node.args])
+    raise ValueError("unsupported expression")
+
+
+def tool_calculator(expression):
+    try:
+        val = _safe_eval(ast.parse(str(expression), mode="eval").body)
+        return f"{expression} = {val}"
+    except Exception as e:
+        return f"Could not evaluate '{expression}': {e}"
+
+
+def tool_datetime(timezone="UTC"):
+    now = datetime.datetime.now(datetime.timezone.utc)
+    return f"Current UTC date/time: {now.strftime('%A, %d %B %Y, %H:%M UTC')}"
+
+
+_WMO = {0: "clear sky", 1: "mainly clear", 2: "partly cloudy", 3: "overcast", 45: "fog", 48: "rime fog",
+        51: "light drizzle", 53: "drizzle", 55: "dense drizzle", 61: "light rain", 63: "rain",
+        65: "heavy rain", 71: "light snow", 73: "snow", 75: "heavy snow", 80: "rain showers",
+        81: "rain showers", 82: "violent rain showers", 95: "thunderstorm", 96: "thunderstorm w/ hail"}
+
+
+def tool_weather(location):
+    try:
+        g = requests.get("https://geocoding-api.open-meteo.com/v1/search",
+                         params={"name": location, "count": 1}, headers=UA, timeout=15).json()
+        if not g.get("results"):
+            return f"No location found for '{location}'."
+        r = g["results"][0]
+        lat, lon = r["latitude"], r["longitude"]
+        place = ", ".join(filter(None, [r.get("name"), r.get("admin1"), r.get("country")]))
+        w = requests.get("https://api.open-meteo.com/v1/forecast",
+                         params={"latitude": lat, "longitude": lon,
+                                 "current": "temperature_2m,relative_humidity_2m,weather_code,wind_speed_10m"},
+                         headers=UA, timeout=15).json()
+        c = w.get("current", {})
+        desc = _WMO.get(c.get("weather_code"), "unknown")
+        return (f"Weather in {place}: {c.get('temperature_2m')}°C, {desc}, "
+                f"humidity {c.get('relative_humidity_2m')}%, wind {c.get('wind_speed_10m')} km/h.")
+    except Exception as e:
+        return f"Weather lookup failed: {e}"
+
+
+def tool_wikipedia(query):
+    try:
+        s = requests.get("https://en.wikipedia.org/w/api.php", headers=UA, timeout=15,
+                         params={"action": "query", "list": "search", "srsearch": query,
+                                 "format": "json", "srlimit": 1}).json()
+        hits = s.get("query", {}).get("search", [])
+        if not hits:
+            return f"No Wikipedia article found for '{query}'."
+        title = hits[0]["title"]
+        e = requests.get("https://en.wikipedia.org/w/api.php", headers=UA, timeout=15,
+                         params={"action": "query", "prop": "extracts", "exintro": 1, "explaintext": 1,
+                                 "titles": title, "format": "json"}).json()
+        pages = e.get("query", {}).get("pages", {})
+        extract = next(iter(pages.values()), {}).get("extract", "")
+        return f"Wikipedia — {title}: {extract[:800]}" if extract else f"Found '{title}' but no summary."
+    except Exception as e:
+        return f"Wikipedia lookup failed: {e}"
+
+
+TOOLS_SPEC = [
+    {"name": "calculator", "description": "Evaluate an arithmetic expression. Supports + - * / ** % and "
+     "sqrt, log, sin, cos, tan, floor, ceil, abs, round, pi, e.",
+     "input_schema": {"type": "object", "properties": {"expression": {"type": "string"}},
+                      "required": ["expression"]}},
+    {"name": "current_datetime", "description": "Get the current date and time (UTC).",
+     "input_schema": {"type": "object", "properties": {"timezone": {"type": "string"}}}},
+    {"name": "weather", "description": "Get the current weather for a city/place name (live).",
+     "input_schema": {"type": "object", "properties": {"location": {"type": "string"}},
+                      "required": ["location"]}},
+    {"name": "wikipedia", "description": "Look up a topic on Wikipedia and get a summary (live).",
+     "input_schema": {"type": "object", "properties": {"query": {"type": "string"}},
+                      "required": ["query"]}},
+]
+EXECUTORS = {"calculator": tool_calculator, "current_datetime": tool_datetime,
+             "weather": tool_weather, "wikipedia": tool_wikipedia}
+
+
+def run_agent(question):
+    import anthropic
+    client = anthropic.Anthropic(api_key=ANTHROPIC_KEY)
+    sysp = ("You are a helpful assistant that answers using the provided tools whenever they help. "
+            "Call tools to get live/precise data instead of guessing. You may call multiple tools. "
+            "When you have enough, give a clear, concise final answer.")
+    msgs = [{"role": "user", "content": question}]
+    trace = []
+    for _ in range(MAX_STEPS):
+        r = client.messages.create(model=ANTHROPIC_MODEL, max_tokens=1024, system=sysp,
+                                   tools=TOOLS_SPEC, messages=msgs)
+        if r.stop_reason == "tool_use":
+            msgs.append({"role": "assistant", "content": r.content})
+            results = []
+            for b in r.content:
+                if b.type == "tool_use":
+                    out = EXECUTORS.get(b.name, lambda **k: "unknown tool")(**b.input)
+                    trace.append({"tool": b.name, "input": b.input, "result": out[:400]})
+                    results.append({"type": "tool_result", "tool_use_id": b.id, "content": out})
+            msgs.append({"role": "user", "content": results})
+        else:
+            text = "".join(b.text for b in r.content if b.type == "text")
+            return text.strip(), trace
+    return "I reached the step limit before finishing — try a simpler question.", trace
+
+
+app = Flask(__name__)
+app.config["MAX_CONTENT_LENGTH"] = 512 * 1024
+
+
+@app.route("/")
+def home():
+    return Response(PAGE, mimetype="text/html")
+
+
+@app.route("/api/ask", methods=["POST"])
+def api_ask():
+    q = (request.get_json(force=True).get("question") or "").strip()[:1000]
+    if not q:
+        return jsonify(error="Ask a question."), 400
+    if not ANTHROPIC_KEY:
+        return jsonify(error="Set ANTHROPIC_API_KEY on the server to run the agent."), 200
+    try:
+        answer, trace = run_agent(q)
+    except Exception as e:
+        import sys; print("agent error:", repr(e), file=sys.stderr, flush=True)
+        return jsonify(error="The agent hit an error — please try again."), 200
+    return jsonify(answer=answer, trace=trace)
+
+
+PAGE = """<!doctype html><html lang="en"><head><meta charset="utf-8">
+<title>Tool-Using Agent</title>
+<meta name="viewport" content="width=device-width,initial-scale=1">
+<style>
+:root{--primary:#4f46e5;--accent:#7c3aed;--ink:#171633;--bg:#f1f0fb;--card:#fff;--muted:#6b6a89;--line:#e5e3f5}
+*{box-sizing:border-box}html,body{height:100%}
+body{margin:0;font-family:'Segoe UI',system-ui,-apple-system,sans-serif;color:var(--ink);
+ background:radial-gradient(140% 90% at 50% 0%,#fff,var(--bg) 60%);display:flex;justify-content:center}
+.app{width:100%;max-width:820px;min-height:100dvh;display:flex;flex-direction:column;padding:0 16px}
+header{padding:26px 4px 12px;display:flex;align-items:center;gap:13px}
+.hic{width:46px;height:46px;border-radius:13px;display:grid;place-items:center;font-size:23px;flex:none;color:#fff;
+ background:linear-gradient(135deg,var(--primary),var(--accent));box-shadow:0 10px 26px -10px rgba(79,70,229,.6)}
+header h1{margin:0;font-size:23px;font-weight:800;letter-spacing:-.4px}
+header p{margin:2px 0 0;color:var(--muted);font-size:13.5px}
+.card{background:var(--card);border:1px solid var(--line);border-radius:16px;padding:16px;box-shadow:0 6px 22px rgba(23,22,51,.05)}
+.inrow{display:flex;gap:10px}
+#q{flex:1;border:0;outline:none;font-size:15px;color:var(--ink);font-family:inherit;background:transparent;padding:4px}
+.go{border:0;border-radius:12px;padding:11px 22px;font-size:15px;font-weight:600;cursor:pointer;color:#fff;background:linear-gradient(135deg,var(--primary),var(--accent));transition:.15s}
+.go:hover{filter:brightness(1.08)}.go:disabled{opacity:.5;cursor:default}
+.ex{display:flex;flex-wrap:wrap;gap:8px;margin-top:12px}
+.chip{background:var(--card);border:1px solid var(--line);border-radius:20px;padding:7px 12px;font-size:12px;cursor:pointer;transition:.15s;color:var(--muted)}
+.chip:hover{border-color:var(--accent);color:var(--accent)}
+.out{margin:18px 0;display:none}.out.show{display:block}
+.trace{margin-bottom:14px}
+.step{display:flex;gap:10px;align-items:flex-start;font-size:13px;padding:9px 12px;border:1px solid var(--line);border-radius:11px;margin-bottom:8px;background:#faf9ff}
+.step .tn{font-weight:700;color:var(--primary);font-family:ui-monospace,monospace;font-size:12px;white-space:nowrap}
+.step .ta{color:var(--ink)}.step .tr{color:var(--muted);margin-top:3px}
+.answer{font-size:16px;line-height:1.6;white-space:pre-wrap}
+.lbl{font-size:11px;text-transform:uppercase;letter-spacing:.5px;color:var(--muted);font-weight:600;margin:0 2px 8px}
+.spin{display:inline-flex;gap:6px;padding:14px 2px}.spin span{width:9px;height:9px;border-radius:50%;background:var(--accent);opacity:.5;animation:bd 1.2s infinite}
+.spin span:nth-child(2){animation-delay:.2s}.spin span:nth-child(3){animation-delay:.4s}
+@keyframes bd{0%,60%,100%{transform:translateY(0);opacity:.35}30%{transform:translateY(-6px);opacity:1}}
+.foot{text-align:center;font-size:10.5px;color:var(--muted);padding:16px 0 22px}.foot b{color:#4a487a}
+</style></head>
+<body><div class="app">
+<header><div class="hic">🛠️</div><div><h1>Tool-Using Agent</h1>
+ <p>Ask anything — it calls live tools (calculator, weather, Wikipedia, clock) and shows its work.</p></div></header>
+<div class="card">
+ <div class="inrow">
+  <input id="q" placeholder="e.g. What's a 15% tip on $47.80, and the weather in Paris?" autofocus>
+  <button class="go" id="go" onclick="ask()">Ask →</button>
+ </div>
+ <div class="ex" id="ex"></div>
+</div>
+<div class="out" id="out">
+ <div class="trace" id="trace"></div>
+ <div class="lbl">Answer</div>
+ <div class="card"><div class="answer" id="answer"></div></div>
+</div>
+<div class="foot">ReAct loop · live keyless tools (Open-Meteo + Wikipedia) · <b>GritAI</b></div>
+</div><script>
+const EXAMPLES=["What's a 15% tip on $47.80, and what's the weather in Paris?",
+ "Who invented the World Wide Web, and how many days ago was Jan 1 2000?",
+ "What's the square root of 20736, and what's the weather in Tokyo?",
+ "Summarize what an octopus is, then tell me the current UTC time."];
+const TICON={calculator:'🧮',current_datetime:'🕐',weather:'🌦️',wikipedia:'📚'};
+const $=id=>document.getElementById(id);
+const q=$('q'),go=$('go'),out=$('out');
+function esc(s){return String(s==null?'':s).replace(/[&<>]/g,c=>({'&':'&amp;','<':'&lt;','>':'&gt;'}[c]));}
+$('ex').innerHTML=EXAMPLES.map(e=>'<span class="chip">'+esc(e)+'</span>').join('');
+$('ex').querySelectorAll('.chip').forEach(c=>c.onclick=()=>{q.value=c.textContent;ask();});
+function ask(){if(go.disabled)return;const text=q.value.trim();if(!text){q.focus();return;}
+ go.disabled=true;go.textContent='Thinking…';out.classList.add('show');
+ $('trace').innerHTML='<span class="spin"><span></span><span></span><span></span></span>';$('answer').textContent='';
+ fetch('/api/ask',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({question:text})})
+ .then(r=>r.json()).then(d=>{
+  if(d.error){$('trace').innerHTML='';$('answer').textContent=d.error;return;}
+  $('trace').innerHTML=(d.trace||[]).map(s=>{const ic=TICON[s.tool]||'🔧';
+    return '<div class="step"><div class="tn">'+ic+' '+esc(s.tool)+'</div><div><div class="ta">'+
+      esc(JSON.stringify(s.input))+'</div><div class="tr">→ '+esc(s.result)+'</div></div></div>';}).join('')||
+    '<div class="step"><div class="tr">(answered directly, no tools needed)</div></div>';
+  $('answer').textContent=d.answer;
+ }).catch(()=>{$('trace').innerHTML='';$('answer').textContent='Something went wrong — please try again.';})
+ .finally(()=>{go.disabled=false;go.textContent='Ask →';});
+}
+q.addEventListener('keydown',e=>{if(e.key==='Enter')ask();});
+</script></body></html>"""
+
+
+if __name__ == "__main__":
+    backend = "Claude API" if ANTHROPIC_KEY else "NO KEY (set ANTHROPIC_API_KEY)"
+    print(f"Tool-Using Agent on http://127.0.0.1:{PORT}  [backend: {backend}]", flush=True)
+    app.run(host="0.0.0.0", port=PORT, threaded=True)

requirements.txt

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+flask>=3.0
+requests>=2.31
+anthropic>=0.40