Tell your agent of choice to read the preamble of all the documents in the skills directory, and tell it that when it has a task that matches one of the preambles, it should read the rest of the relevant file for full instructions.

There are far fewer dependencies for skills than for MCP. Even a model that knows nothing about tool use beyond how to run a shell command, and has no support for anything else can figure out skills.

I don't know what you mean regarding explicitly referencing other skills - Claude at least is smart enough that if you reference a skill that isn't even properly registered, it will often start using grep and find to hunt for it to figure out what you meant. I've seen this happen regularly while developing a plugin and having errors in my setup.