I'm a little confused about the relationship of Skills and just plain tools. It seems like a lot of skills might just be tools. Or, they might rely on calling sets of tools with some instructions.

But aren't the tool definitions and skill definitions in different places? How do you express the dependency? Can skills say they require command line access, python, tool A, and tool B, and when you load the skill it sets those as available tool calls?

Skills seem to have code packaged in. They have added pdf, excel support using skills.