mcp

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Build MCP (Model Context Protocol) servers to extend Claude's capabilities with database access, API integrations, or custom tools.

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[Developer Tools]

When & Why to Use This Skill

This Claude skill provides a comprehensive framework for building Model Context Protocol (MCP) servers, enabling Claude to interact directly with external data sources and tools. By implementing MCP, developers can extend Claude's capabilities beyond text processing to include real-time database querying, API orchestration, and local file system management, creating a highly integrated and actionable AI agent environment.

Use Cases

  • Database Integration: Enable Claude to execute secure, read-only SQL queries on live databases (e.g., PostgreSQL) to perform real-time data analysis and reporting.
  • Custom API Wrappers: Build servers that allow Claude to fetch data from or trigger actions in third-party services like weather APIs, CRMs, or internal company tools.
  • Local File System Access: Grant Claude the ability to list, read, and manage local project files, facilitating automated code reviews and documentation updates.
  • Workflow Automation: Create custom tools that Claude can call to trigger complex workflows, such as CI/CD pipelines or automated record creation in project management software.
namemcp
descriptionBuild MCP (Model Context Protocol) servers to extend Claude's capabilities with database access, API integrations, or custom tools.

MCP

Build MCP servers that give Claude access to external tools and data.

What is MCP?

Model Context Protocol lets you create servers that Claude can call:

  • Query databases
  • Call APIs
  • Access file systems
  • Run custom tools

When to Build an MCP Server

  • You want Claude to access live data (not just files)
  • You're repeating the same API calls manually
  • You want Claude to take actions (create records, trigger workflows)

Project Setup

mkdir my-mcp-server && cd my-mcp-server
pnpm init
pnpm add @modelcontextprotocol/sdk zod
pnpm add -D typescript @types/node tsx

// package.json
{
  "type": "module",
  "scripts": {
    "dev": "tsx watch src/index.ts",
    "build": "tsc",
    "start": "node dist/index.js"
  }
}

// tsconfig.json
{
  "compilerOptions": {
    "target": "ES2022",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "outDir": "dist",
    "strict": true,
    "esModuleInterop": true
  },
  "include": ["src"]
}

Basic Server Template

// src/index.ts
import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js'
import { z } from 'zod'

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

// Define a tool
server.tool(
  'hello',
  'Say hello to someone',
  { name: z.string().describe('Name to greet') },
  async ({ name }) => ({
    content: [{ type: 'text', text: `Hello, ${name}!` }],
  })
)

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

Common Patterns

Database Access (Postgres)

import pg from 'pg'

const pool = new pg.Pool({
  connectionString: process.env.DATABASE_URL,
})

server.tool(
  'query',
  'Run a read-only SQL query',
  { sql: z.string().describe('SELECT query to run') },
  async ({ sql }) => {
    if (!sql.trim().toLowerCase().startsWith('select')) {
      return { content: [{ type: 'text', text: 'Only SELECT queries allowed' }] }
    }
    const result = await pool.query(sql)
    return { content: [{ type: 'text', text: JSON.stringify(result.rows, null, 2) }] }
  }
)

API Wrapper

server.tool(
  'get_weather',
  'Get current weather for a city',
  { city: z.string() },
  async ({ city }) => {
    const res = await fetch(`https://api.weather.com/current?city=${city}`)
    const data = await res.json()
    return { content: [{ type: 'text', text: JSON.stringify(data, null, 2) }] }
  }
)

File System Access

import { readdir, readFile } from 'fs/promises'

server.tool(
  'list_projects',
  'List projects in studio-manager',
  {},
  async () => {
    const dirs = await readdir('/Users/brew/studio-manager', { withFileTypes: true })
    const projects = dirs.filter(d => d.isDirectory()).map(d => d.name)
    return { content: [{ type: 'text', text: projects.join('\n') }] }
  }
)

Claude Desktop Config

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "my-server": {
      "command": "node",
      "args": ["/path/to/my-mcp-server/dist/index.js"],
      "env": {
        "DATABASE_URL": "postgres://..."
      }
    }
  }
}

Restart Claude Desktop after changes.

Testing

# Run server directly to test
echo '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | pnpm start

Security Notes

  • Validate all inputs with Zod
  • Limit database access to SELECT only (unless intentional)
  • Don't expose secrets in tool responses
  • Consider rate limiting for external APIs

Reference