LangGraph Minimal ReAct Agent (Calculator-only)

This repository provides a minimal ReAct-style agent built with LangGraph. It includes a single calculator tool (powered by numexpr) for arithmetic expressions, keeping everything simple for testing and extension.

Graph entrypoint: src/react_agent/graph.py:graph (via langgraph.json)

Screenshot:

Requirements

• Python 3.11+
• uv (fast Python package manager)
  • Install: pip install uv (or see https://github.com/astral-sh/uv)

Setup

1. Create your .env:

cp .env.example .env

2. Add your model API key in .env. Default in this template is OpenAI:

OPENAI_API_KEY=your-openai-key

3. Install dependencies with uv:

uv sync

Run in LangGraph Studio

Start the dev server:

uv run langgraph dev

Notes:

• langgraph.json maps the graph:

  {
    "dependencies": ["."],
    "graphs": {
      "agent": "./src/react_agent/graph.py:graph"
    },
    "env": ".env"
  }

• Studio will load the graph and hot-reload your local edits.

Quick CLI test (optional)

uv run python examples/minimal_demo.py

This will send a prompt like “What is (25 * 4) + 3?” and the agent should call the calculator tool to compute the answer.

Customize

• Tools: add functions in src/react_agent/tools.py and include them in TOOLS.
• Model: change default in src/react_agent/configuration.py (format provider/model, default is openai/gpt-4o-mini-2024-07-18) or configure in Studio.
• Prompt: edit the minimal prompt in src/react_agent/prompts.py.

Credits

Template maker: basim akram

License

See LICENSE.