Modern Business Central projects rarely live in isolation—APIs are the connective tissue that lets the ERP exchange data with e‑commerce sites, CRMs, data warehouses, IoT back ends, and more. This post walks developers through how to consume external and internal APIs from Microsoft Dynamics 365 Business Central (BC), covering authentication, performance, error handling, and troubleshooting. Highlights include OAuth 2.0 patterns, choosing between the classic HttpClient data type and the new AL Rest Client, and real‑world code snippets.