An API is a general interface for software systems. MCP is a specific protocol designed for AI applications that need to discover and use tools, resources, and prompts.
In practice
Many MCP servers call normal APIs behind the scenes. MCP gives AI clients a consistent way to see available capabilities, while the underlying service may still use REST, GraphQL, SQL, or another API.
What to watch
MCP does not replace all APIs. It is best understood as an AI-friendly layer around tools and data sources.