What is an MCP server?

The short answer

A chat model on its own can only read what you paste in and write text back. An MCP server sits between the assistant and some other system, and offers the assistant a list of actions it may take there, such as "run this SQL query" or "open this web page". The assistant decides when to use them; your app asks you before it does, unless you have told it not to.

Anthropic published the Model Context Protocol in November 2024 as an open standard. Since then Claude, ChatGPT, Cursor, VS Code, Windsurf and many other apps have added support, so one server works in all of them. Before MCP, every app needed its own plugin for every tool.

The three parts

When the host starts, it connects to each server you configured and asks what it offers. The server answers with a list of tools, each with a name, a description and the inputs it takes. The model reads those descriptions and calls a tool when it fits the conversation; the server does the work and sends the result back as text or data.

What a server can offer

• Tools: actions the model can call, such as search_issues, take_screenshot or run_query. This is what most servers are for.
• Resources: data the app can read into the conversation, such as a file, a table schema or a document.
• Prompts: ready-made instructions the server suggests, which some apps show as slash commands.

Most apps today use tools far more than the other two, so when people compare servers they usually mean "which tools does it give my assistant".

Local and remote servers

A local server is a program your app starts on your own computer, usually with npx (Node.js), uvx (Python) or Docker, and talks to over standard input and output. A remote server is a web address run by someone else, reached over HTTP, often with a sign-in. Local suits anything that touches your files or network; remote suits services like Notion or GitHub where the vendor runs it for you. Our remote vs local guide goes through the trade-offs.

{
  "mcpServers": {
    "playwright": {
      "command": "npx",
      "args": ["-y", "@playwright/mcp@latest"]
    }
  }
}

{
  "mcpServers": {
    "context7": {
      "url": "https://mcp.context7.com/mcp"
    }
  }
}

What people use them for

Before you install one

A local server runs with your user account, so it can do whatever you can. Check three things first: that the package in the config is published by the project itself (copycat names exist on npm and PyPI), that the repository is maintained, and what the tools can change. Start database and cluster servers in read-only mode where they offer one. Our checklist for vetting a server covers this step by step.

Questions