One of the most critical challenges for the success of the Metaverse is interoperability amongst its virtual platforms and worlds. In this context, application programming interfaces (APIs) are essential. This study analyzes a sample of 15 Metaverse platforms. In the first step, the availability of publicly accessible APIs was examined. For those platforms offering an API, i.e., Decentraland, Second Life, Voxels, Roblox, Axie Infinity, Upland, and VRChat, the available API contents were collected, analyzed, and presented in the paper. The results show that only a few Metaverse platforms offer APIs at all. In addition, the available APIs are very diverse and heterogeneous. Information is somewhat fragmented, requiring access to several APIs to compile a comprehensive data set. Thus, standardized APIs will enable better interoperability and foster a more seamless and immersive user experience in the Metaverse.