The Model Context Protocol (MCP) is deceptively simple on the surface but powerful underneath. To truly master your AI development environment, you need to understand its three-tier architecture.
The Three Pillars of MCP
MCP isn’t just “connecting an AI to a database.” It involves three distinct roles:
1. The Host (The Application)
This is the user-facing application where the interaction happens.
- Examples: Claude Desktop App, Cursor IDE, Zed Editor.
- Role: The Host provides the user interface (the chat window) and manages the connection lifecycle. It decides when to call a tool.
2. The Client (The Protocol Handler)
Often embedded within the Host, the Client is the piece of code that speaks the actual JSON-RPC protocol.
- Role: It maintains a 1:1 connection with the Server. It handles capability negotiation (e.g., “Hey Server, do you support prompts or just tools?“).
3. The Server (The Data Provider)
This is a standalone process running on your machine.
- Examples: A Python script querying SQLite, a Node.js app reading files.
- Role: The Server exposes Resources (data), Prompts (templates), and Tools (executable functions).
How Data Flows
When you ask Claude: “Summarize the last 3 commit messages in this repo”
- User types prompt into Host (Claude).
- Host sends the prompt to the LLM.
- LLM realizes it needs git info. It generates a Tool Call.
- Host passes this request to the MCP Client.
- MCP Client forwards the request to the Git MCP Server.
- MCP Server executes
git log -n 3. - MCP Server returns the text output to the Client.
- Client hands it back to the Host.
- Host gives the data to the LLM.
- LLM generates the final summary for the User.
Why This Separation Matters
This architecture is the key to MCP’s flexibility.
- Security: The Server runs in its own process. You can sandbox it. If the Server crashes, it doesn’t crash your IDE.
- Language Agnostic: Your Client can be in Rust (Zed), your Server in Python, and they talk over standard input/output (stdio).
- Reusability: Because the interface is standardized, the same “Git Server” works for Claude, Cursor, and any future AI tool.
Configuring the Connections
This is where things get tricky for users. Every Host needs to know:
- Where the Server executable is located.
- What arguments to launch it with.
- Environment variables (API keys).
This configuration is typically stored in JSON files. And managing these JSON files across multiple Hosts is why we built Vibe Manager. It orchestrates these connections so you don’t have to manually edit the wiring diagram every time you want to add a new tool.