As large language models (LLMs) like OpenAI’s GPT-4 continue to evolve, so do the frameworks and techniques that make them easier to use and integrate into real-world applications. Whether you're building a chatbot, automating document analysis, or creating intelligent agents that can reason and use tools, understanding how to interact with LLMs is key. This post walks through a practical journey of using both the OpenAI API and LangChain — exploring everything from basic prompt engineering to building modular, structured, and even parallelized chains of functionality.