In 2015, Rebilly faced a challenge when integrating with a larger enterprise that relied on a third-party ERP for integrations, which threatened to delay or even stall the process. To address this, Rebilly adopted an API-Design First approach by co-designing a partner-specific API with the enterprise using a private GitHub repository and a continuous integration system to build ReDoc-rendered API documentation. This collaboration involved iterative adjustments to the API definitions based on feedback from business analysts, ultimately creating a more familiar and necessary API for the partner. The clear documentation and shared understanding accelerated development and integration, leading to a successful and lucrative $22 million enterprise deal. The use of visually appealing API documentation was crucial in engaging non-technical stakeholders and ensuring a professional presentation, demonstrating the effectiveness of the API-First Design methodology.