The document discusses the importance of data normalization when integrating APIs. It notes that APIs often have inconsistent data formats and endpoints that are not standardized. This can make APIs difficult to reuse and maintain. The document proposes normalizing data into a common structure and configuration-based transformations to map different APIs and data formats to this normalized structure. This allows applications to have a unified view of data across APIs and makes the APIs more reusable and interchangeable. It also discusses using asynchronous interactions and message buses to link normalized data across APIs rather than application-level logic.