APIUsage is a detailed tracking and analysis tool that helps users manage their OpenAI API usage and costs. By providing insights into daily API consumption, it allows users to understand the costs for different models like ChatGPT, GPT-4, and Whisper. APIUsage helps in optimizing API key utilization, making it easier to handle expenses for various projects, teams, or applications by using separate keys for each. The tool ensures transparent and manageable API billing and consumption, thereby avoiding unnecessary expenditures.