比較
Agent Skills と MCP：どちらを出すか
スキルはファイルで手順を教えます。MCP は動いているツールを出します。多くのチームは両方が要ります。境界ははっきり分けます。
更新 2026-09-18 · 7 分
An Agent Skill teaches a procedure from files. MCP exposes live tools with input and output schemas. They are not rivals. They sit on opposite sides of a boundary: markdown versus a running process.
Side by side
| Agent Skill | MCP | |
|---|---|---|
| Payload | SKILL.md plus optional files | A server the agent can call |
| Discovery | YAML description | Tool names and schemas |
| Best for | Checklists, house style, multi-step writing | Tickets, databases, browsers, billed APIs |
| Fails when | You hide a live API inside prose | You stuff a 20-page playbook into a tool description |
A clean split
Use a skill to decide whether and in what order. Use MCP to do the privileged action. Example: a research skill tells the agent how to cite sources. An HTTP or browser MCP actually fetches the page.
If you are unsure, start with a skill. Promote a step to MCP only when the agent must touch a system that is not the working tree. The MCP Builder skill and the Skill Creator skill exist for those two jobs.