This tutorial gives a brief overview of how the Fabric Transfer API works, and how you can use it for your own mods. For any question, please go to the #fluid-volume-api-debating channel on the discord server.

The API Lookup system allows blocks and items to expose functionality (called “API“s) in a flexible manner. Example use cases include: blocks that contain items such as chests, blocks that contain fluids such as tanks, blocks that can be wrenched, blocks that can be colored, blocks that contain mana, items that contain fluids, and so on…

For Forge users, it is similar to the Capability system, but without data storage or event dispatch.

Link to the documentation. Read the BlockApiLookup and ItemApiLookup class documentation for a usage example.