Payabli, a next-generation payments infrastructure platform, has significantly improved its API documentation process by adopting Fern Definition, an alternative to the OpenAPI Specification. The shift to Fern has reduced the time spent on API spec management from 30% to 5%, allowing the team to focus more on enhancing the developer experience with interactive documentation features. Fern's flexibility in handling complex payment APIs and its support for custom components and styling has enabled Payabli to create a more engaging and navigable documentation site. This includes innovative tools like a transaction lifecycle explorer and an ACH timeline calculator, which help developers understand complex concepts interactively. The single-source documentation approach facilitated by Fern also ensures consistency across API references, Postman collections, SDKs, and code examples. This transformation in documentation strategy has led to increased developer productivity and quicker feature adoption, aligning with Payabli's goal of being the easiest payments company to integrate with.