Why
The Terminal API is foundational to in-person payments. Its legacy structure made it hard to understand, maintain, and integrate with modern developer tooling. Making it accessible mattered for long-term platform scalability and developer trust.What
The Terminal API is a non-REST API based on the nexo retailer protocol. For years, its only reference lived on a single page assembled from many HTML files. It was hard to navigate and incompatible with the OpenAPI-based API Explorer.How
I mapped the full API structure by reconciling the official nexo PDF specification, the existing documentation, and the OpenAPI requirements of the API Explorer tooling. I coordinated between the team that owned the Terminal API implementation and the platform team responsible for API reference pipelines. We created a Python script that generates OpenAPI specs the tooling could consume. We introduced a new API Explorer page type that presents the API structure by request type.Result
The migration brought a critical legacy API into the standard developer experience without changing its underlying protocol. It reduced long-term maintenance risk and improved discoverability for a globally used payments API.© 2026 Strahinja Milošević | Author of all-maker.com, a part of the tech writing blog webring