Model Context Protocol (MCP) - Claude Code Templates

Model Context Protocol (MCP) is an open standard that enables Claude Code to connect with external data sources, APIs, and services. MCP servers act as bridges between Claude and the outside world.

What Are MCPs?

MCPs are JSON configuration files (.json) that define server connections:

Server configuration - How to start and connect to MCP servers
Command and arguments - What to execute (npm packages, binaries, scripts)
Environment variables - Configuration and API keys
Capabilities - What tools and resources the server provides

MCP servers run as separate processes and communicate with Claude Code via stdio (standard input/output).

MCP Architecture

MCP configuration lives in .mcp.json at your project root:

{
  "mcpServers": {
    "fetch": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-fetch"]
    },
    "postgres": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-postgres"],
      "env": {
        "POSTGRES_CONNECTION_STRING": "postgresql://user:pass@localhost/db"
      }
    }
  }
}

Configuration Structure

Field	Required	Description
`command`	Yes	Executable to run (e.g., `npx`, `node`, `python`)
`args`	Yes	Array of command arguments
`env`	No	Environment variables for the server
`description`	No	Human-readable description (removed during installation)

MCP Categories

Access web content and external APIs:

web-fetch - HTTP requests, web scraping, API calls
github-integration - GitHub API access (repos, issues, PRs)
slack-integration - Slack API for messages and channels

npx claude-code-templates@latest --mcp web/web-fetch

Capabilities:

Fetch web pages and parse HTML
Make REST API requests
Download files and images
Parse JSON and XML responses

Direct database access and queries:

postgresql-integration - PostgreSQL database access
mysql-integration - MySQL database operations
supabase - Supabase client with auth and storage
neon - Neon serverless Postgres

npx claude-code-templates@latest --mcp database/postgresql-integration

Capabilities:

Execute SQL queries
Inspect database schemas
Run migrations
Analyze query performance

Code analysis and development utilities:

deepgraph-react - React component analysis
deepgraph-nextjs - Next.js project insights
deepgraph-typescript - TypeScript codebase analysis
sentry - Error tracking and monitoring

npx claude-code-templates@latest --mcp devtools/deepgraph-react

Capabilities:

Analyze component dependencies
Find unused code
Track imports and exports
Visualize code structure

Headless browser control:

playwright - Browser automation with Playwright
puppeteer - Chrome automation
selenium - Multi-browser automation

npx claude-code-templates@latest --mcp browser_automation/playwright

Capabilities:

Navigate web pages
Fill forms and click buttons
Take screenshots
Extract data from dynamic sites

Enhanced file operations:

filesystem-access - Extended file system operations
memory-integration - Persistent memory and notes

npx claude-code-templates@latest --mcp filesystem/filesystem-access

Capabilities:

Read/write files with advanced options
Watch file changes
Search file contents
Manage permissions

Note-taking and productivity tools:

obsidian - Obsidian vault access
notion - Notion workspace integration
google-drive - Google Drive file access

npx claude-code-templates@latest --mcp productivity/obsidian

Capabilities:

Read/write notes
Search across documents
Manage tags and links
Export content

Real-World Examples

Example 1: Web Fetch MCP

File: .mcp.json

{
  "mcpServers": {
    "fetch": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-fetch"]
    }
  }
}

Usage in Claude Code:

Fetch the latest release notes from https://api.github.com/repos/anthropics/claude-code/releases/latest

Claude automatically uses the MCP server to make the HTTP request.

Example 2: PostgreSQL Database MCP

File: .mcp.json

{
  "mcpServers": {
    "postgres": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-postgres"],
      "env": {
        "POSTGRES_CONNECTION_STRING": "postgresql://localhost/mydb"
      }
    }
  }
}

Usage in Claude Code:

Query the users table and show me all users created in the last 7 days

Claude connects to PostgreSQL and executes the query.

Example 3: GitHub Integration MCP

File: .mcp.json

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

Usage in Claude Code:

List all open issues in the main repository and summarize the top 3 by reactions

Claude uses the GitHub API via MCP to fetch and analyze issues.

Installing MCPs

Single MCP

npx claude-code-templates@latest --mcp web-fetch

The MCP configuration merges with your existing .mcp.json.

Multiple MCPs

npx claude-code-templates@latest \
  --mcp web-fetch \
  --mcp postgresql-integration \
  --mcp github-integration

With Category Prefix

npx claude-code-templates@latest --mcp database/postgresql-integration

MCP servers are downloaded on-demand when first used. No manual installation required beyond configuration.

Environment Variables

Many MCPs require API keys or connection strings:

Secure Configuration

DON’T hardcode secrets:

{
  "env": {
    "API_KEY": "sk-1234567890"  // ❌ Bad: exposed in git
  }
}

DO use environment variables:

{
  "env": {
    "API_KEY": "${API_KEY}"  // ✅ Good: reads from shell environment
  }
}

Set variables in your shell:

export API_KEY="sk-1234567890"

Or use .env files (add to .gitignore):

# .env
POSTGRES_CONNECTION_STRING=postgresql://localhost/db
GITHUB_TOKEN=ghp_your_token

Never commit API keys, database passwords, or tokens to version control. Use environment variables or secret management tools.

MCP Server Types

NPM Packages

Most official MCPs are npm packages:

{
  "command": "npx",
  "args": ["-y", "@modelcontextprotocol/server-name"]
}

The -y flag auto-installs packages without prompting.

Python Scripts

{
  "command": "python",
  "args": ["-m", "mcp_server_name"]
}

Requires the Python package to be installed: pip install mcp-server-name

Custom Executables

{
  "command": "/path/to/custom-server",
  "args": ["--config", "./config.json"]
}

Docker Containers

{
  "command": "docker",
  "args": [
    "run",
    "--rm",
    "-i",
    "custom/mcp-server:latest"
  ]
}

MCP Capabilities

MCP servers can provide:

1. Tools

Functions that Claude can call:

// Example: web-fetch provides
fetch(url: string, options?: RequestInit)
html_to_markdown(html: string)
download_file(url: string, path: string)

2. Resources

Data that Claude can read:

// Example: postgres provides
schema://tables          // List all tables
schema://tables/{name}   // Table schema
query://{sql}            // Query results

3. Prompts

Pre-built prompt templates:

// Example: github provides
analyze-repo    // Analyze repository structure
review-pr       // Review pull request

Creating Custom MCP Servers

You can build custom MCP servers:

Choose Implementation

Use the MCP SDK for TypeScript or Python:

npm install @modelcontextprotocol/sdk

Implement Server

Create server with tools and resources:

import { Server } from '@modelcontextprotocol/sdk/server/index.js';

const server = new Server({
  name: 'my-server',
  version: '1.0.0'
});

server.tool('my-tool', async (args) => {
  // Tool implementation
  return { result: 'success' };
});

Configure in .mcp.json

Add your server configuration:

{
  "mcpServers": {
    "my-server": {
      "command": "node",
      "args": ["./mcp-servers/my-server.js"]
    }
  }
}

Test

Use your custom server in Claude Code:

Use my-tool to process the data

For detailed MCP development guides, see MCP Documentation.

MCP Best Practices

1. Security First

Never hardcode credentials
Use environment variables for secrets
Validate all inputs
Limit server permissions
Use read-only access when possible

2. Error Handling

Servers should handle errors gracefully:

server.tool('fetch-data', async (args) => {
  try {
    const response = await fetch(args.url);
    if (!response.ok) {
      throw new Error(`HTTP ${response.status}`);
    }
    return await response.json();
  } catch (error) {
    return {
      error: true,
      message: error.message
    };
  }
});

3. Resource Management

Close connections properly
Implement timeouts
Clean up resources
Handle server shutdown gracefully

4. Documentation

Document your MCP tools clearly:

server.tool(
  'search-database',
  {
    description: 'Search database with SQL query',
    parameters: {
      query: { type: 'string', description: 'SQL query to execute' },
      limit: { type: 'number', description: 'Max results', default: 100 }
    }
  },
  async (args) => { /* ... */ }
);

Troubleshooting MCPs

Server Won’t Start

Check the command and arguments:

{
  "command": "npx",
  "args": ["-y", "@modelcontextprotocol/server-fetch"]
}

Test manually:

npx -y @modelcontextprotocol/server-fetch

Environment Variables Not Working

Ensure variables are exported:

export DATABASE_URL="postgresql://localhost/db"
echo $DATABASE_URL  # Should print the URL

Check variable syntax:

{
  "env": {
    "DATABASE_URL": "${DATABASE_URL}"  // Must use ${VAR} syntax
  }
}

Connection Errors

Verify network access:

Database servers are running
Firewall allows connections
Credentials are correct
Connection strings are properly formatted

Permission Denied

Ensure executable permissions:

chmod +x ./mcp-servers/my-server.js

MCP vs Claude Code Tools

MCP Servers	Claude Code Tools
External services	Built-in capabilities
Requires configuration	Always available
Custom capabilities	Standard operations
Network/database access	File system access
Community-built	Official tools

MCPs extend Claude’s capabilities beyond the built-in tools. Use them to connect Claude with your specific services and data sources.

Official MCP Servers

Anthropics maintains official MCP servers:

@modelcontextprotocol/server-fetch - HTTP requests
@modelcontextprotocol/server-filesystem - File operations
@modelcontextprotocol/server-github - GitHub API
@modelcontextprotocol/server-postgres - PostgreSQL
@modelcontextprotocol/server-sqlite - SQLite

Browse all at MCP Registry.

Next Steps

Browse MCPs

Explore 65+ available MCPs

MCP Documentation

Official MCP specification

Create MCP Server

Build custom MCP servers

Settings

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Get Started

Core Concepts

Guides

Tools

Advanced

​What Are MCPs?

​MCP Architecture

​Configuration Structure

​MCP Categories

​Real-World Examples

​Example 1: Web Fetch MCP

​Example 2: PostgreSQL Database MCP

​Example 3: GitHub Integration MCP

​Installing MCPs

​Single MCP

​Multiple MCPs

​With Category Prefix

​Environment Variables

​Secure Configuration

​MCP Server Types

​NPM Packages

​Python Scripts

​Custom Executables

​Docker Containers

​MCP Capabilities

​1. Tools

​2. Resources

​3. Prompts

​Creating Custom MCP Servers

​MCP Best Practices

​1. Security First

​2. Error Handling

​3. Resource Management

​4. Documentation

​Troubleshooting MCPs

​Server Won’t Start

​Environment Variables Not Working

​Connection Errors

​Permission Denied

​MCP vs Claude Code Tools

​Official MCP Servers

​Next Steps

Browse MCPs

MCP Documentation

Create MCP Server

Settings

Build docs developers (and LLMs) love

What Are MCPs?

MCP Architecture

Configuration Structure

MCP Categories

Real-World Examples

Example 1: Web Fetch MCP

Example 2: PostgreSQL Database MCP

Example 3: GitHub Integration MCP

Installing MCPs

Single MCP

Multiple MCPs

With Category Prefix

Environment Variables

Secure Configuration

MCP Server Types

NPM Packages

Python Scripts

Custom Executables

Docker Containers

MCP Capabilities

1. Tools

2. Resources

3. Prompts

Creating Custom MCP Servers

MCP Best Practices

1. Security First

2. Error Handling

3. Resource Management

4. Documentation

Troubleshooting MCPs

Server Won’t Start

Environment Variables Not Working

Connection Errors

Permission Denied

MCP vs Claude Code Tools

Official MCP Servers

Next Steps