Functionary provides a declarative way to register custom tools — JavaScript functions encapsulating API calls, database queries, or business logic. It wraps an LLM interaction to analyze user prompts, determine which tools to execute, and parse the tool outputs back into conversational responses. The framework supports memory, error handling, and chaining of actions, offering hooks for pre- and post-processing. Developers can quickly spin up agents capable of dynamic function orchestration without boilerplate, enhancing control over AI-driven workflows.