Xero, an online accounting software, offers a variety of functionalities including invoice processing, expense management, and bill payments, making it beneficial for integration with other applications. The Xero API provides a range of publicly available endpoints that facilitate these integrations by allowing access to data across resources such as purchase orders and bank transactions. Integrating Xero with systems like ticketing or file storage can streamline processes, enhance data access, and improve workflow efficiencies. To authenticate with Xero's API, developers need a client ID and client secret, which are used to obtain access tokens for API requests. The document also highlights best practices for managing Xero's rate and volume limits, like filtering data requests and using webhooks for real-time updates. Additionally, Merge's Unified API platform is discussed as a comprehensive solution for adding multiple accounting integrations, including Xero, to a product, offering features such as Common Models, advanced data sync, and integration observability to ease integration management.