Use MCP Servers
An MCP server gives your AI app tools it can call: search your CRM, query a database, open a pull request. These guides show you how to connect servers to the app you already use, how sign-in works, and what to do when a server won't show up.
New to MCP? Start with MCP vs API, then pick your app below.
What is MCP
MCP stands for Model Context Protocol, the open standard that connects AI apps to tools and data. How it works, its parts, and what changed in 2026.
MCP vs API
How MCP differs from a plain API and from model function calling, how they fit together, and when you need neither.
MCP clients
What an MCP client is, and how Claude, ChatGPT, Cursor, VS Code, Codex and other AI apps compare on local servers, remote servers, OAuth and MCP Apps.
Claude Code
Add a local or remote MCP server to Claude Code with claude mcp add, pick a scope, share it in .mcp.json, sign in with OAuth from /mcp, and remove it.
Codex
Add local and remote MCP servers to Codex with codex mcp add or config.toml, then sign in to OAuth servers. Works in the CLI, IDE extension and app.
Claude Desktop
Find Claude Desktop's config file on macOS, Windows and Linux, add local and remote MCP servers, sign in with OAuth, and read the logs when a server won't connect.
Cursor
Connect an MCP server to Cursor with mcp.json. Covers file locations, local and remote servers, OAuth sign-in, and how to check it's working.
ChatGPT
Add a remote MCP server to ChatGPT from the Plugins page, sign in with OAuth, choose which tools it can use, and check that it works.
VS Code and Copilot
Add a local or remote MCP server to VS Code with a servers entry in mcp.json, keep tokens out of the file, and confirm Copilot Chat calls its tools.
Gemini CLI
Add local and remote MCP servers to Gemini CLI in settings.json or with gemini mcp add, sign in over OAuth, and check they connect.
Windsurf
Add local and remote MCP servers to Windsurf's Cascade agent with mcp_config.json, sign in with OAuth, and check that the tools load.
OAuth sign-in
What happens when a remote MCP server asks you to sign in with OAuth, how it differs between AI apps, and how to sign out or sign in again.
Fix connection errors
Find the real error behind an MCP server that won't connect, read the app's log, and fix the causes in Claude, Cursor, VS Code, Claude Code and Codex.