AI Agents with Function Calling: Build Tools LLMs Can Use

Function calling transforms LLMs from simple text generators into active AI agents capable of executing code, searching the web, and calling APIs. By outputting structured JSON to invoke predefined functions, these agents replace hallucinated facts with verified data from APIs. This process enables multi-step workflows, persistent state, and standardized interfaces. Developers can build complete agent frameworks using Python 3.10+ and OpenRouter or Groq API keys to implement production patterns involving planning, memory, and error recovery.