Function calling is transforming large language models (LLMs) from static knowledge generators into dynamic, interactive agents capable of real-world tasks by enabling them to detect when a user request requires external data or action and produce a structured output specifying which function to call. This capability allows LLMs to integrate real-time data, such as weather information, into their responses by triggering external APIs and updating the conversation context with the retrieved information. The Model Context Protocol (MCP) further enhances function calling by standardizing the connection between AI models and data sources, simplifying integration, and establishing a framework for AI interoperability. This advancement is paving the way for agentic AI systems that can plan multi-step workflows, adapt their decisions based on intermediate results, and maintain contextual memory across interactions. As function calling evolves, it holds the potential to enable autonomous agents that collaborate with humans to tackle complex challenges, marking a significant shift in the landscape of human-AI interaction.