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Skills vs MCP vs Plugins - What's the Difference?

Fazm Team··2 min read
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Skills vs MCP vs Plugins

These three concepts get mixed up constantly. They serve different purposes and work at different layers of an AI agent's architecture. Here is how they actually differ.

Skills Are Prompts

A skill is a set of instructions that gets injected into a conversation. When you activate a skill, you are giving the agent a detailed prompt about how to handle a specific task - what steps to follow, what format to use, what to watch out for.

Skills do not give the agent new capabilities. They guide how it uses existing ones. Think of them as reusable expertise that you do not have to type out every time.

For example, a "code review" skill might tell the agent to check for security issues first, then performance, then style. The agent already knows how to read code - the skill just directs its attention.

MCP Servers Are Tools

MCP (Model Context Protocol) servers expose actual functions that the agent can call. A Gmail MCP server lets the agent read and send emails. A browser MCP server lets it click buttons and fill forms. A filesystem MCP server lets it read and write files.

Without the MCP server, the agent literally cannot perform these actions. With it, the agent has new capabilities it did not have before.

Plugins Are Platform Integrations

Plugins are specific to a platform and often bundle multiple capabilities together. A Slack plugin might include both tools (send messages, read channels) and UI elements (sidebar panels, slash commands). They are tightly coupled to the host application.

Why This Matters

When someone says "I built a plugin for my agent," ask what they actually built. If it is a prompt template, it is a skill. If it exposes new callable functions, it is an MCP server. If it integrates deeply with a specific platform's UI and APIs, it is a plugin.

Knowing the difference helps you pick the right approach for what you are building.

Fazm is an open source macOS AI agent. Open source on GitHub.

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