What Are MCP Servers? A Guide to the Model Context Protocol

January 1, 2026 · 7 min read

If you’ve been following developments in AI tooling, you’ve probably heard about MCP servers. The Model Context Protocol is quietly revolutionizing how AI assistants interact with external tools, databases, and APIs. But what exactly is it, and why should you care?

Let’s break it down.

The Problem MCP Solves

AI assistants like Claude are incredibly capable at reasoning, writing, and analyzing information. But they have a limitation: they can’t directly interact with your systems.

Want Claude to:

• Query your database?
• Check your calendar?
• Send a Slack message?
• Deploy code to your server?
• Look up information in your company wiki?

Without MCP, this requires complex integrations, custom code, and often isn’t possible at all.

What Is MCP?

The Model Context Protocol is an open standard that allows AI assistants to communicate with external tools and data sources through a standardized interface.

Think of it like this:

• USB standardized how devices connect to computers
• HTTP standardized how browsers talk to web servers
• MCP standardizes how AI assistants talk to tools

How MCP Works: The Architecture

MCP uses a client-server model:

The Components

The Communication Flow

Here’s what happens when an AI uses an MCP tool:

1. User asks AI: "What meetings do I have tomorrow?"

2. AI recognizes it needs calendar data

3. AI calls MCP server: get_calendar_events(date: "2026-01-02")

4. MCP server queries Google Calendar API

5. MCP server returns: [{title: "Team standup", time: "9:00 AM"}, ...]

6. AI responds: "You have a team standup at 9:00 AM tomorrow..."

The user never sees the MCP communication—they just get a helpful answer that includes real data from their calendar.

What MCP Servers Can Do

MCP servers expose three types of capabilities:

1. Tools (Functions the AI Can Call)

Tools are actions the AI can perform:

2. Resources (Data the AI Can Access)

Resources are read-only data sources:

3. Prompts (Reusable Templates)

Prompts are pre-defined conversation starters:

Real-World MCP Server Examples

Database Query Server

Let your AI assistant query your database safely:

// Simplified MCP server for database queries
const server = new MCPServer({
  name: "database-query",
  version: "1.0.0"
});

server.addTool({
  name: "query_customers",
  description: "Search customers by name or email",
  parameters: {
    search: { type: "string", description: "Search term" }
  },
  handler: async ({ search }) => {
    const results = await db.query(
      "SELECT name, email FROM customers WHERE name LIKE ? OR email LIKE ?",
      [`%${search}%`, `%${search}%`]
    );
    return results;
  }
});

Slack Integration Server

Post messages and read channels:

server.addTool({
  name: "send_slack_message",
  description: "Send a message to a Slack channel",
  parameters: {
    channel: { type: "string", description: "Channel name" },
    message: { type: "string", description: "Message to send" }
  },
  handler: async ({ channel, message }) => {
    await slack.chat.postMessage({
      channel: channel,
      text: message
    });
    return { success: true };
  }
});

File System Server

Read and write files (with appropriate permissions):

server.addTool({
  name: "read_file",
  description: "Read contents of a file",
  parameters: {
    path: { type: "string", description: "File path" }
  },
  handler: async ({ path }) => {
    // Security: validate path is within allowed directory
    const safePath = validatePath(path, allowedDirectory);
    return await fs.readFile(safePath, 'utf-8');
  }
});

Building Your First MCP Server

Here’s a minimal MCP server in TypeScript:

import { Server } from "@modelcontextprotocol/sdk/server";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio";

const server = new Server({
  name: "my-first-mcp-server",
  version: "1.0.0"
}, {
  capabilities: {
    tools: {}
  }
});

// Define a simple tool
server.setRequestHandler("tools/list", async () => ({
  tools: [{
    name: "get_weather",
    description: "Get current weather for a city",
    inputSchema: {
      type: "object",
      properties: {
        city: { type: "string", description: "City name" }
      },
      required: ["city"]
    }
  }]
}));

// Handle tool calls
server.setRequestHandler("tools/call", async (request) => {
  if (request.params.name === "get_weather") {
    const city = request.params.arguments.city;
    // In reality, call a weather API here
    return {
      content: [{
        type: "text",
        text: `Weather in ${city}: 72°F, Sunny`
      }]
    };
  }
});

// Start the server
const transport = new StdioServerTransport();
await server.connect(transport);

Running Your Server

MCP servers typically run as local processes and communicate via stdio (standard input/output) or HTTP:

# Install dependencies
npm install @modelcontextprotocol/sdk

# Run the server
node my-mcp-server.js

Configure your AI client (Claude Desktop, VS Code, etc.) to connect to the server, and you’re ready to go.

Security Considerations

MCP includes several security features:

Best Practices

1. Principle of Least Privilege - Only expose what’s necessary
2. Validate All Inputs - Treat AI-provided arguments as untrusted
3. Rate Limiting - Prevent runaway API calls
4. Sandboxing - Limit file system and network access
5. Logging - Record all tool calls for audit

Popular MCP Servers

The MCP ecosystem is growing quickly. Here are some popular servers:

Find more at the MCP Servers Repository.

When Should You Build an MCP Server?

Consider building an MCP server when:

The Future of MCP

MCP is still early, but adoption is accelerating. Anthropic (Claude’s creator) open-sourced the protocol, and major AI tools are adding support:

• Claude Desktop - Native MCP support
• VS Code - MCP extension ecosystem
• Cursor - MCP integration for coding
• Custom apps - Easy to add via SDK

As AI assistants become more capable, the ability to connect them to real-world tools becomes critical. MCP provides that bridge.

Get Started

Ready to explore MCP? Here’s where to go:

Need Help Building an MCP Server?

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