FireFunction V1, developed by Fireworks, is an advanced function calling model that outperforms GPT-4 in speed while maintaining similar accuracy for real-world applications. Built on the Mixtral framework, it offers open weights and is designed for structured output generation and decision-making, with improved response accuracy for multilingual inputs and complex JSON specifications. The model allows for dynamic agent applications through function calls, enabling external API integration, and ensures structured output adherence. FireFunction's speed advantage is significant, achieving up to 4x faster response times compared to GPT-4 Turbo, making it particularly effective for use cases requiring fast decision-making and model routing. Currently available for free during its limited beta period, FireFunction can be integrated into existing systems with minimal changes and is aimed at developers looking to leverage its capabilities for enhanced LLM applications.