MCP Server Integration

What is MCP?

The Model Context Protocol (MCP) is an open standard that lets AI models connect to external tools and data sources. Think of it as USB for AI — a universal plug that connects Claude to your entire stack.

Without MCP, Claude can only read files and run terminal commands. With MCP, it can query databases, post to Slack, create GitHub issues, search the web, manage your calendar, and interact with any API — all natively.

How MCP Servers Work

An MCP server is a small program that exposes tools (actions Claude can take) and resources (data Claude can read). Claude discovers available tools at startup and can call them during conversations.

The connection is configured in .mcp.json at your project root:

{
  "mcpServers": {
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": { "GITHUB_TOKEN": "$GITHUB_TOKEN" }
    }
  }
}

Essential MCP Servers

The most valuable MCP integrations for development teams:

• GitHub: Create issues, review PRs, manage repos — all from conversation
• Slack: Post updates, read channels, send DMs to team members
• Notion: Query databases, create pages, update project documentation
• PostgreSQL/SQLite: Run queries, inspect schemas, analyze data directly
• Web Search: Search the web and fetch page content in real time
• Claude Peers: Let multiple Claude instances communicate and coordinate

Building a Custom MCP Server

When you need Claude to interact with an internal tool or API, build a custom MCP server. The official SDK makes this straightforward:

• Define tools — each tool has a name, description, and JSON schema for parameters
• Implement handlers — write the function that executes when Claude calls the tool
• Register in .mcp.json — point Claude at your server with the command to start it
• Test locally — run your server and verify Claude can discover and call your tools

Security Considerations

MCP servers run with the same permissions as your user account. Key security rules:

• Never hardcode API keys — use environment variables referenced with $VAR_NAME
• Use read-only tokens when possible (e.g., GitHub read-only PAT for code review)
• Audit which tools each server exposes — remove any you don't need
• Keep servers updated — MCP is evolving rapidly with security patches

Practical Exercise

Set up two MCP servers for your project:

1. Add the GitHub MCP server to your .mcp.json
2. Create a GITHUB_TOKEN with repo read permissions
3. Test by asking Claude to list your recent PRs or create an issue
4. Add a second server (Slack, Notion, or web search)
5. Verify Claude can discover and use tools from both servers simultaneously