The process of building an API integration is unique due to differences in how API providers approach pagination, authentication, and rate limits, as well as varying integration requirements for each product or internal workflow. To scope an API integration project, one must research the API provider's available endpoints, define build requirements, outline responsibilities among team members, assign timelines for each phase, and present the plan to stakeholders. This process involves several steps, including investigating API documentation, defining efforts based on endpoint details, planning for integration monitoring workflows, and clarifying roles and responsibilities within the team. By following these steps, teams can successfully scope and implement API integrations, and tools like Merge's Unified API can simplify this process by allowing developers to add hundreds of integrations through a single API, saving time and improving product reliability.