Is something like Claude Desktop an MCP host or client?

[christianareas-postman]

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Discussion Topic

If I'm reading the docs correctly, Claude Desktop is an MCP host:

https://modelcontextprotocol.io/docs/learn/architecture#participants

But it's listed here as a client:

https://modelcontextprotocol.io/clients#claude-desktop-app

Should the page be called:

Example Hosts
A list of applications that support MCP integrations

[mozmo15]

Its technically both, depending on how you see "Claude desktop"
The link you put I think explains it well, its mostly the source for my own information

Technically, you dont really need any AI involved for MCP, its just a communication standard. But its one designed to "plug into" AI apps. Where it plugs into is the MCP host. The MCP host has to have an MCP client inside it to talk to the server.

Think of it this way, the "host" is what makes use of information that its client may fetch from an MCP server. For example, you talk to an LLM which is connected to an MCP server that fetches live weather data, and you ask it about the day's forecast. The host (LLM app) has an MCP client connected to this weather MCP server; it sees that it has access to a tool that can get you this information, so it tells it's MCP-client to make a tool call and processes the result. Then it runs its own logic to talk back to you. The host is the smart manager in this process, the MCP-client is just a utility it has access to that communicates with a specific server based on a messaging standard. The host can have many such MCP-clients at a time, for each server you may want to connect to

[kiminobreakfast]

Hello, I have a question: How can a single host create multiple clients to connect to multiple servers? If the client and server connections are one-to-one, how can multiple servers be used simultaneously?

[mozmo15]

@kiminobreakfast Sorry I just saw this. An MCPClient and MCPServer connection are indeed "one-to-one", but an mcp-host can and does create multiple MCPClient instances, and an mcp-server application also creates multiple MCPServer instances. I think the confusing part is that the language implies each mcp-server or mcp-client instance is a running application on its own, when what they actually are is an object instance running within the same application/process. Calling an mcp-server application an "MCP Server" can be misleading because in reality it is an application that is creating an instance of an MCPServer object for every client connection. This is why inspite of a 1:1 relationship an mcp-server application can connect to and communicate with multiple clients simultaneously.

I hope this wasn't confusing. Just remember, an mcp-host creates multiple client objects if you're connecting to multiple servers (ex: if using javascript, there are multiple MCPClient javascript objects at the host, one for each server you want to connect to) and an mcp-server will create multiple server objects for each client (one MCPServer object for each incoming client request). You can check the examples folder in the sdk repos for more details

[isheng-eqi]

You are right — the naming is inconsistent, and the /clients page should indeed be called /hosts (or "Example Hosts"). Here is the definitive answer.

The correct terminology

Claude Desktop is an MCP host. Period.

The architecture is:

┌─────────────────────────────┐
│      MCP Host               │
│  (Claude Desktop, Cursor,   │
│   VS Code, Claude Code)     │
│                             │
│  ┌───────────────────────┐  │
│  │    MCP Client         │──┼──→ MCP Server A (filesystem)
│  │  (one per server)     │  │
│  └───────────────────────┘  │
│  ┌───────────────────────┐  │
│  │    MCP Client         │──┼──→ MCP Server B (github)
│  └───────────────────────┘  │
│  ┌───────────────────────┐  │
│  │    MCP Client         │──┼──→ MCP Server C (database)
│  └───────────────────────┘  │
└─────────────────────────────┘

• Host = the application that orchestrates AI + tools (Claude Desktop, Cursor, etc.)
• Client = a connection object inside the host, one per remote server. It speaks the MCP protocol to one specific server.
• Server = the remote process that provides tools, resources, and prompts.

Each host creates one MCP Client per server it connects to. This is why you can connect Claude Desktop to 5 different MCP servers simultaneously — the host creates 5 client instances.

Why the /clients page is confusing

The page at modelcontextprotocol.io/clients lists host applications (Claude Desktop, Cursor, Zed, etc.), not MCP clients. It was named from the user's perspective ("apps I can use as a client of MCP services") rather than from the protocol's perspective ("applications that act as MCP hosts").

In the protocol's own architecture diagram at modelcontextprotocol.io/docs/learn/architecture, the correct terms are "Host," "Client," and "Server." The /clients page predates the formalization of "host" terminology and has not been updated.

Should the page be renamed?

Yes. "Example Hosts" or "Applications that support MCP" would be more accurate. The current name conflates the user-facing concept ("I want to use MCP") with the protocol concept ("host vs client"). This is a documentation bug, not a protocol ambiguity.

Bonus: why "host" and not just "client"?

The distinction matters because an MCP host does more than just connect to servers. A host:

1. Manages the LLM interaction loop (receiving user input, sending prompts, processing responses)
2. Discovers and exposes tools from all connected servers to the LLM
3. Routes tool calls to the correct server's client
4. Handles user consent and security boundaries

An MCP client is just a protocol-level TCP/stdio connection. The host is the full application. Conflating them would be like calling a web browser a "TCP client" — technically true but useless for understanding the architecture.