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What is MCP?

MCP (Model Context Protocol) is an open standard created by Anthropic that defines how AI models communicate with external tools. It's like a "USB for AI": a universal connector that any tool can implement.

With MCP, Claude Code can access resources beyond your local file system: PostgreSQL databases, REST APIs, the web browser, Slack, GitHub, Jira, and any service that has an MCP server.

How it works

An MCP server is a process (local or remote) that exposes:

Tools: functions Claude can call (e.g., run SQL, search Slack).
Resources: data Claude can read (e.g., DB schema, documentation).
Prompts: specialized instructions for specific tasks.

Adding an MCP server

MCP servers are configured in .claude/settings.json :

TerminalCode

{
  "mcpServers": {
    "postgres": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-postgres",
               "postgresql://localhost/midb"],
      "env": {}
    },
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_xxxxxxxx"
      }
    }
  }
}

Or add servers directly from the CLI:

TerminalCode

claude mcp add <nombre> -- <comando> [args...]

# Ejemplo: servidor de PostgreSQL
claude mcp add postgres -- npx -y @modelcontextprotocol/server-postgres \
  "postgresql://localhost/midb"

# Ejemplo: servidor de filesystem (solo lectura)
claude mcp add files -- npx -y @modelcontextprotocol/server-filesystem \
  /ruta/al/directorio

Popular MCP servers

Managing MCP servers

TerminalCode

# Listar servidores configurados
claude mcp list

# Ver detalles de un servidor
claude mcp get postgres

# Eliminar un servidor
claude mcp remove postgres

# Dentro de Claude Code, ver servidores activos:
/mcp

MCP server scopes

MCP servers have three possible scopes:

Local (default): available only in the current project. Saved in .claude/settings.json .
User: available across all your projects. Saved in ~/.claude/settings.json . Add --scope user to the command.
Project: shared with the team via version control.

TerminalCode

# Añadir servidor a nivel de usuario (global)
claude mcp add --scope user github -- npx -y @modelcontextprotocol/server-github

Creating your own MCP server

Any script that implements the MCP protocol can be a server. Anthropic provides SDKs for Python and TypeScript:

TerminalCode

# TypeScript
npm install @modelcontextprotocol/sdk

# Python
pip install mcp

Minimal TypeScript example

TerminalCode

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

const server = new Server({ name: "mi-servidor", version: "1.0.0" }, {
  capabilities: { tools: {} }
});

server.setRequestHandler("tools/list", async () => ({
  tools: [{
    name: "saludar",
    description: "Saluda al usuario",
    inputSchema: {
      type: "object",
      properties: { nombre: { type: "string" } },
      required: ["nombre"]
    }
  }]
}));

server.setRequestHandler("tools/call", async (request) => {
  if (request.params.name === "saludar") {
    return { content: [{ type: "text", text: `Hola, ${request.params.arguments.nombre}!` }] };
  }
});

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

MCP in the cloud vs local

MCP servers can run locally (as a process on your machine) or in the cloud (connected via HTTP/SSE). Claude Code supports both:

TerminalCode

# Servidor local (stdio)
{
  "command": "node",
  "args": ["./mi-servidor-mcp.js"]
}

# Servidor remoto (HTTP/SSE)
{
  "url": "https://mi-servidor.com/mcp",
  "headers": { "Authorization": "Bearer TOKEN" }
}