What is an MCP server?

An MCP server is a small program that exposes tools, resources, and prompts to an AI client. The client speaks the Model Context Protocol; the server does the actual work, such as reading a database or opening a browser.

There are two common shapes. A local server runs on your machine, usually through npx, uvx, or Docker, and talks over stdio. A remote server is a URL that speaks streamable HTTP or the older SSE transport.

MCPpedia lists both. Each page shows the registry name, the package or URL, the environment variables, and a config you can paste into a client. "Registry" means the official MCP registry has a record. "Official" means the namespace or repository belongs to a known vendor. Those are different claims, and the trust score treats them differently.