The medium is the message. Pick the one that says what your product means, try it live, then drop the matching Agent Skill into your repo so your coding agent builds it for you.
The router skill, which teaches your agent to choose a medium, plus every medium, kind, and composition. You pick which in the prompt.
One skill each. A lane is a folder. A kind is a data domain inside a lane whose concerns diverge; it is a folder too, named lane-kind, and shows up under its lane.
Two or more mediums bound together. The skill teaches the binding and points at the mediums for the parts.