Skill vs MCP
Teaching the agent something it can already do, versus giving it something new to reach for
Skill
A folder of instructions kept out of context until needed. It teaches the current agent how and when to use capabilities it already has. No running process, no new connection, just knowledge loaded on demand into the existing session.
MCP
A live connection to a running server that exposes new tools the agent did not have before. It adds capability, not just instructions, a way to reach a database, an API, or a system the agent could not touch on its own.
Which one do you actually need
Use a Skill when the agent already has what it needs and just requires the right procedure or convention, a deploy checklist, a house style, a known workaround. Use MCP when the agent needs to reach something genuinely new, a live system, a database, an external service it has no other way to touch. Many real setups use both together: MCP supplies the tool, a Skill supplies the instructions for using it well.