This document discusses how communication service providers (CSPs) are leveraging open APIs. It outlines several open API initiatives led by organizations like the Linux Foundation and TM Forum. The TM Forum has defined 54 APIs for CSP operational functions. Initiatives like ONAP and MEF are aligning on external APIs. The document suggests CSPs could expose APIs for infrastructure, core communications services, IT services, and identity management. Open APIs may help CSPs adopt a platform business model and remain relevant to enterprise and consumer customers. It poses questions about adoption of open APIs by traditional OSS/BSS systems and vendors.