MCP vs REST API
MCP does not make REST obsolete. They solve different interface problems.
REST is an application API style
REST APIs expose domain operations through HTTP resources and methods. They are broadly supported, easy to monitor, and excellent for frontend/backend and service-to-service communication.
MCP is an AI capability protocol
MCP adds conventions designed for AI hosts: capability discovery, tool schemas and descriptions, resources, prompts, and protocol-specific interaction patterns. An MCP server frequently calls existing REST APIs behind the scenes.
A common production architecture
AI Host → MCP Server → Existing REST API → Business Service
This preserves your business API while giving AI clients a model-friendly interface. The MCP server can translate tool arguments into API calls, apply policy, normalize errors, and return concise results.
When REST alone is enough
- You control both caller and server.
- The integration is not model-driven.
- You do not need discovery or reusable AI tool schemas.
- Your app has only a small number of fixed endpoints.
When MCP adds value
- Multiple AI hosts should reuse the integration.
- You want a capability catalog for agents.
- You need standardized tool/resource semantics.
- You expect the AI integration layer to evolve independently of the underlying API.
Do not expose your entire REST API as hundreds of MCP tools automatically. Tool surfaces should be designed around meaningful agent tasks, least privilege, and clear semantics.