GetPack

Posted on Sep 30 Originally published at getpack.fr

Skills vs MCP connectors vs plugins: the difference explained

#ai #mcp #claude #beginners

First published in GetPack Magazine, sourced guides to use AI well as a student.

A skill is a folder of instructions (a SKILL.md file, sometimes with scripts) that Claude loads when your request matches it: it teaches Claude how to do a task. An MCP connector is a connection to an outside service (your files, your calendar, a database) through the Model Context Protocol: it gives the AI access to data and actions. A plugin is a package that bundles skills, connectors, commands and agents so you can install them in one go. In ChatGPT, connectors are now called "apps", and ChatGPT also has skills and plugins that follow the same logic.

In short: the skill is the method, the connector is the access, the plugin is the packaging. A skill fetches no data on its own, a connector has no idea how you like to work, and a plugin adds nothing beyond what it contains. A connector sees the data of the service you plug in; a skill or a plugin can run code. Only install what comes from a source you know.

The official definition, minus the jargon

Anthropic has a page that compares all three. MCP connectors "give Claude access to a tool or data source", skills "teach it how to do a task the way you or your team does it", and plugins "package skills, MCP connectors, commands, and agents into one unit" (Connectors, skills, and plugins). The help center puts it another way: MCP connects Claude to external services and data sources, while skills provide procedural knowledge.

The skill: a method, not access

A skill is a folder. At minimum it holds a SKILL.md with a header (name and description) and a Markdown body describing the steps to follow, plus optional reference files and scripts.

Its big advantage is progressive loading. According to the Agent Skills documentation, Claude only keeps each skill's name and description in context, about 100 tokens. The body loads only when your request matches; extra files are read only when the instructions point to them, and for a script, only its output enters the conversation.

On claude.ai, skills run in Claude's code sandbox, so "Code execution and file creation" must be on under Settings, then Capabilities (Skills overview). In Claude Code, a skill is just a folder in ~/.claude/skills/ or .claude/skills/. The steps are in our guide to installing a skill, and writing one is covered in Writing your own Claude skill. Skills follow an open specification, Agent Skills, so a skill written for Claude can work in other tools that adopt it.

The MCP connector: access, not a method

The official site defines MCP as "an open-source standard for connecting AI applications to external systems" and compares it to a USB-C port: one shared plug instead of a different cable per device. Claude, ChatGPT, VS Code and Cursor all support it (modelcontextprotocol.io).

A connector is an MCP server exposing three kinds of building blocks (Architecture overview): tools, functions the AI calls to take action; resources, context data such as a file's contents; and prompts, reusable interaction templates. The server runs remotely at the provider, or locally on your computer. It acts inside a real service with your account, which is both its strength and its risk. To plug one in without code, follow Connect an MCP connector to Claude; to see what's under the hood, build your first MCP server.

The plugin: a package, not a new capability

For Claude Code, a plugin is "a directory of skills, agents, hooks, MCP servers, or other components that Claude Code installs and loads as one unit" (Plugins overview). A manifest, .claude-plugin/plugin.json, gives it a name, which then works as a prefix: /my-plugin:review.

Most plugins come from a marketplace. The word is misleading: it's a catalog, a repository with a marketplace.json file listing plugins and where to fetch them. Claude Code adds Anthropic's official one the first time you start an interactive session; browse it with /plugin, in the Discover tab.

Skills, hooks and MCP servers work perfectly well on their own: a plugin is for installing or sharing several at once. On claude.ai and the desktop app, you add plugins from Customize, then Plugins, and each app loads only what it supports: skills, commands and connectors in chat, plus agents in Cowork and Claude Code (Plugins).

Comparison table

	Skill	MCP connector (app in ChatGPT)	Plugin
What it is	A folder of `SKILL.md` instructions, sometimes with scripts	A connection to an MCP server that opens a service	A package of skills, connectors, commands, agents, hooks
Where it runs	Code sandbox on claude.ai; your machine in Claude Code	The provider's server, or your computer (local)	Your Claude account, or your machine for Claude Code
What it can do	Follow a method or format; run a bundled script	Read, search and act in the service	Whatever its components do, nothing more
Risks and data	Rigged instructions or scripts; full network access in Claude Code	Sees the connected account's data; prompt injection	Can run code with your user permissions
Student example	Turning lecture notes into flashcards, same format every time	Searching open-access theses from the chat	A revision pack: a notes skill plus a papers connector

When to use which

Ask one question: what is the AI missing?

The method. You repeat the same instructions every session ("fill-in-the-blank questions, no answers straight away, a quiz at the end"): that's a skill.
The access. You keep copy-pasting from a database, a drive or a calendar: that's a connector, which fetches up-to-date information at the source.
Both, to share. You're putting together a kit for your project group or student society: that's a plugin.

A word of caution: a skill doesn't "know" your documents, it only sees what you give Claude or what a connector brings back. And a plugin doesn't connect its connectors by itself: you still sign in with your own account.

On academic integrity, the type of tool changes nothing. A good study skill works like a coach: it explains, asks questions, checks your work and lets you do the producing. Before using one on graded work, check your institution's rules on AI use.

Where to find them: claude.ai, Claude Desktop, Claude Code, ChatGPT

claude.ai. Everything lives under Customize: Skills, Connectors, Plugins. You turn a connector on per conversation, through "+" then Connectors; the directory shows a Verified or Community label on each listing (Get started with connectors). To run a skill by hand, type / in the message box.

Claude Desktop. Same page, plus local connectors installed as desktop extensions (MCPB format), which run on your computer.

Claude Code. Skills in ~/.claude/skills/, connectors with claude mcp add, plugins with /plugin. Connectors and plugins on your claude.ai account carry over when you sign in with that account; anything you install from the command line stays on your machine. New to it? Start with Claude Code for beginners.

ChatGPT. What used to be called connectors are now "apps". You connect them from Settings, then Plugins, and call them with @ or "+" (Connected apps in ChatGPT). ChatGPT plugins can contain skills, apps or both (Plugins in ChatGPT). Skills are currently limited to eligible Business, Enterprise, Healthcare and Edu workspaces (Skills in ChatGPT). Plugging in your own MCP server requires developer mode, which OpenAI calls "powerful but dangerous": its developer docs open it to Plus, Pro, Business, Enterprise and Education accounts on the web (Developer mode), while the help center describes full support, including write actions, as a beta for Business, Enterprise and Edu. Check what your account shows.

Safety: who sees what

A connector sees your data. That's its job. Anthropic sums up its advice in five points: only connect to trusted servers, review requested permissions carefully, be aware of prompt injections, monitor changes in tool behavior, and keep an eye on the actions Claude takes (custom connectors). Each connector tool can be set to "Always allow", "Needs approval" or "Blocked": keep approval on for anything that writes, sends or deletes.

In ChatGPT, an enabled app may receive context from your conversations and your memory, your IP address and your approximate location. On the Free, Plus, Go and Pro plans, OpenAI may use information accessed from apps to train its models if "Improve the model for everyone" is on.

A skill can run code. The Agent Skills documentation recommends using only skills you created or got from Anthropic: a malicious skill can steer Claude into running code unrelated to its stated purpose, up to leaking data. Skills you upload or that others share with you aren't reviewed by Anthropic, so open the SKILL.md and its files before turning one on.

A plugin stacks those risks. In Claude Code, an installed plugin can execute arbitrary code with your user privileges, and its hooks run outside the sandbox (Plugin security and trust). A marketplace's name tells you who publishes the catalog, not what each plugin does. On claude.ai, directory plugins go through a security scan and human review; plugins added by URL or uploaded yourself don't. At OpenAI too, the "OpenAI Verified" badge doesn't replace your own review.

Our take: the real dividing line is trust. A skill is text you can read in two minutes. A connector is an open door to one of your accounts. A plugin can hold both, plus code that runs on your machine. The more a tool touches your data or your computer, the more its origin matters.

What this means for you

Whether you're revising, coding or researching, start from what's missing, not from whatever tool is trending. Read what you install, add one connector at a time and for a clear reason, enable connectors only in the conversations that need them, and keep manual approval for anything that changes your data.

FAQ

What is a Claude skill, in one sentence?

A folder of instructions, with a SKILL.md file and sometimes scripts, that Claude loads automatically when your request matches its description. It teaches Claude a method without opening any service to it.

What's the difference between a skill and an MCP connector?

The skill tells the AI how to do a task; the connector gives it access to the data or actions of an outside service. They pair well: the connector fetches the papers, the skill says how to turn them into a reading summary.

What exactly is a Claude Code plugin?

A folder bundling skills, agents, hooks and MCP servers, described by .claude-plugin/plugin.json and installed in one go with /plugin, usually from a marketplace. It can run code with your permissions, so only install plugins whose source you know.

Is a ChatGPT connector the same as a Claude connector?

In principle, yes: both rely on MCP. ChatGPT now calls them "apps", connected from Settings, then Plugins. The same MCP server can serve both, but permission and data settings are specific to each platform.

Do I need to code to use skills and connectors?

No: on claude.ai and in ChatGPT, it's all menus. Writing a skill only takes Markdown. Building an MCP server or a plugin with hooks takes some code, and it's the best way to understand what you're plugging in.

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