The short answer
Reach for a Skill when the hard part is the method: the steps, the format, the checks. Reach for MCP when the hard part is getting to a system, like a database, Jira, or an API. Most serious workflows end up using both.
MCP vs Skills side by side
The short version: a Skill is a folder of instructions that anyone can write, and an MCP server is a program that has to run somewhere, usually with credentials.
| Agent Skill | MCP server | |
|---|---|---|
| What it is | A folder: SKILL.md, scripts, reference files | A server that exposes tools, resources, and prompts |
| Where it runs | Instructions inside the agent; scripts on your machine | A local process (stdio) or a remote service (HTTP) |
| When it loads | Name and description first; the rest only when used | Most clients load every tool definition up front |
| What it gives the agent | Judgment: steps, format, a quality bar | Reach: data and actions in other systems |
| Who writes it | Anyone who can write Markdown | Usually developers, often with credentials |
Do you need MCP, a Skill, or both?
Ask what the agent is missing. If it has the material but does the job differently every time, it needs a Skill. If it simply can’t see the data, it needs MCP.
Only a Skill
The agent has what it needs and lacks a method. Example: a brand deck built from notes you paste in.
Only MCP
You need live data once, with no fixed process. “What changed in ticket 482?”
Both
A report you rerun every week on live numbers.
Can Claude Skills use MCP? Yes, here’s how
Yes. A Skill can tell the agent which connected MCP tools to call, in what order, and how to check what comes back. The Skill doesn’t create the connection, so the MCP server has to be set up first. Here’s a weekly report Skill that leans on two of them:
## Steps
1. Use the Linear tools to list issues closed this week.
2. Use the analytics tools to pull weekly active users.
3. Fill the template in references/weekly-report.md.
4. Flag any metric that moved more than 10%.In Codex, a Skill can list the MCP servers it depends on in agents/openai.yaml, and a plugin can ship Skills and MCP connections together.
Can an MCP server serve Skills?
Yes. MCP has an official Skills extension (io.modelcontextprotocol/skills) that lets a server publish Skills in the Agent Skills format. The extension is final, but agents are still adding support, so today most people install Skills as folders.
Which one costs more context?
An idle Skill is cheap. An idle MCP server usually isn’t.
~1 sentence
per installed Skill until it’s used
Every tool
definition from each connected MCP server, loaded up front in most clients
So connect the MCP servers a task actually needs, not every one you have.
Common questions
Do I need MCP if I have Skills?
Only when the agent has to reach a system it can’t get to any other way. A Skill can’t create access; it explains how to use access you already have.
Can Claude Skills use MCP?
Yes. A Skill’s instructions can tell Claude which connected MCP tools to call and what to do with the results.
Can an MCP server expose Skills?
Yes, through MCP’s official Skills extension. Agents are still rolling out support.
Is MCP still relevant now that Skills exist?
Yes. They solve different problems: Skills carry the method, MCP carries the connection.
Sources
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