Model Context Protocol (MCP) is an open standard designed to connect AI applications with the tools and data they need to function. According to the source, MCP operates through a three-part system: a host (the AI app itself, such as Claude, Cursor, ChatGPT, or an agent), a server (a small program that exposes tools, data, or prompts), and a model (which decides what to use but never communicates directly with servers).
The protocol works by having servers declare what capabilities they offer, which the application then presents to the model. When the model wants to use a particular tool or access specific data, the application calls the server and returns the result back to the model. This intermediary approach keeps the model from directly interacting with servers.
MCP differs from REST APIs in its underlying architecture. Rather than using HTTP requests, MCP employs JSON-RPC over stdin/stdout or a single HTTP endpoint, and servers retain the ability to communicate back to hosts. However, JSON-RPC itself is not the full story—it serves as the envelope for the protocol. MCP defines the specific contents of those messages, including the methods available, capability negotiation procedures, transport mechanisms, and authentication schemes.
The source indicates that MCP represents a shift in how AI applications integrate with external resources, providing a standardized framework that goes beyond simple JSON-RPC implementations. By establishing a common protocol, MCP aims to simplify how developers expose functionality to AI models and how those models access and utilize external tools and data sources. This standardization could facilitate broader interoperability across different AI platforms and external services, though the source does not elaborate on specific implementation details or adoption metrics.
Key facts
- MCP is an open standard for connecting AI apps to tools and data
- The protocol uses JSON-RPC over stdin/stdout or a single HTTP endpoint, not REST
- MCP defines methods, capability negotiation, transports, and authentication—not just the JSON-RPC envelope
- Servers declare capabilities that applications present to models
- Models decide what to use but never communicate directly with servers