MCP for Claude Code: Model Context Protocol explained in 5 min
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- Architecture
Model Context Protocol (MCP) for Claude Code in 5 minutes: architecture, real examples, and how MCPs differ from plugins and skills. Fast start guide.
What exactly is MCP?
The Model Context Protocol (MCP) is an open protocol created by Anthropic that lets Claude Code communicate with external services. It's the standard that transforms Claude Code from an isolated assistant into one that's connected to your real environment.
Without MCP, Claude Code can only read and write local files and run shell commands. That's already powerful, but limited to your machine. With MCPs, it can:
- Send a Slack message to your team
- Create a pull request on GitHub
- Run a SQL query on your database
- Take a screenshot of a web page
- Read your emails in Gmail
- Look up documentation for a library
All from your terminal, in plain language.
Architecture: how it works under the hood
MCP relies on a simple and elegant client-server architecture.
You make a request
You write in plain language in Claude Code: "Show me the open GitHub issues on my project".
Claude Code identifies the right tool
Claude Code analyzes your request and determines it needs the GitHub MCP. It knows which tools each MCP exposes thanks to the discovery phase at startup.
The MCP Server translates the request
Claude Code sends a JSON-RPC message to the GitHub MCP Server via stdin/stdout. The MCP server translates this request into actual GitHub API calls.
The result comes back to you
The MCP Server receives the GitHub API response, reformats it, and sends it back to Claude Code. Claude Code presents the result in a readable format and can chain additional actions.
The protocol in detail
MCP uses JSON-RPC 2.0 as its communication format. It's a well-established standard that's lightweight and easy to implement. Communication between Claude Code (the client) and each MCP Server happens via stdin/stdout, using the operating system's standard streams.
Each MCP Server exposes a set of tools that Claude Code can call. For example, the GitHub MCP exposes tools like list_issues, create_pull_request, search_code, etc. At startup, Claude Code queries each configured MCP to discover its available tools.
MCP vs Plugins vs Skills: what's the difference?
These three concepts complement each other but serve different roles.
| MCP | Skills | Plugins | |
|---|---|---|---|
| Role | Connect Claude Code to an external service | Teach a reusable behavior or workflow | Extend Claude Code's internal capabilities |
| Analogy | A USB port to the outside world | A memorized tutorial or recipe | A built-in add-on module |
| Example | GitHub MCP to access repos, PRs, issues | "review-pr" skill for a review process | Formatting, analysis plugins, etc. |
| Configuration | .mcp.json file or settings.json | Markdown file in .claude/commands/ | Via Claude's configuration system |
| Execution | External server (separate process) | Instructions interpreted by Claude Code | Code integrated into Claude Code |
In summary
MCPs give Claude Code hands to interact with the outside world. Skills give it recipes to know what to do. Plugins give it additional internal capabilities. All three combine to create a custom-built assistant.
Key MCP protocol concepts
Tools
Each MCP Server exposes a list of tools. A tool is a function that Claude Code can call. For example:
mcp__github__list_issues: list issues in a repomcp__slack__send_message: send a Slack messagemcp__filesystem__read_file: read a file
Claude Code knows the signature of each tool (its parameters and types) and can call them automatically based on your request.
Resources
Some MCPs also expose resources: data that Claude Code can read but not modify. This is useful for providing additional context (documentation, database schemas, etc.).
Prompts
An MCP can also provide predefined prompts: interaction templates optimized for specific use cases.
Security and permissions
Here are MCP security best practices:
- Principle of least privilege: grant each MCP only the strictly necessary permissions
- Tokens with restricted scopes: use access tokens with minimum rights
- Global configuration for secrets: store your tokens in
~/.claude/settings.json(never in the repo) - Regular review: periodically check which MCPs are configured and what access they have
Next steps
Now that you understand what an MCP is and how it works, let's get hands-on.
- Install and configure an MCP: Step-by-step guide to plug in your first MCP
- Top productivity MCPs: The best MCPs for Gmail, Slack, Calendar, and more
- Top development MCPs: GitHub, Context7, Sentry, databases