What is the difference between an MCP server and an API?

An API is a general interface for software to talk to software; an MCP server is a specific kind of wrapper that exposes an API's capabilities to an AI client through the Model Context Protocol. The key difference is discoverability. A traditional API requires a developer to read documentation and write custom integration code. An MCP server describes its own tools, parameters, and resources in a standard schema, so the AI can call it without prior programming. MCP does not replace APIs; most MCP servers sit in front of existing REST or GraphQL APIs and translate natural-language requests into structured API calls.