How to Connect Claude to Any API Using MCP (Step-by-Step)

Want Claude to send emails, create invoices, manage your CRM, or post to Slack? You need MCP — the Model Context Protocol. This guide shows you how to connect Claude Desktop to any API in under 5 minutes using 0nMCP. What is MCP? MCP (Model Context Protocol) is the standard that lets AI assistants like Claude use external tools. Think of it as USB for AI — one protocol, unlimited devices. Step 1: Install 0nMCP npm install -g 0nmcp Or use npx (no install needed): npx 0nmcp Step 2: Add to Claude Desktop Open your Claude Desktop config: Mac: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%\Claude\claude_desktop_config.json Add this: { "mcpServers" : { "0nMCP" : { "command" : "npx" , "args" : [ "-y" , "0nmcp" ] } } } Restart Claude Desktop. Step 3: Connect Your Services Tell Claude: "Connect my Stripe account" Or manually create connection files in ~/.0n/connections/ : { "$0n" : { "type" : "connection" , "name" : "stripe" }, "service" : "stripe" , "auth" :