Claude Desktop, Cursor, and many other AI tools can already connect to MCP servers. You configure a server, and its tools become available inside the app. So why build your own MCP client?

Because a pre-built host is built for general use. It is great when a person is sitting in front of the tool and choosing what to do. It becomes limiting when MCP is part of your own product.

You might need a Slack bot that can call only approved tools, a scheduled job that reads resources from an internal server, an agent runtime with its own approval rules, or a router that connects to several MCP servers but exposes only the safe tools for the current user.

That product behavior belongs in your host/client layer: authorization, logging, retries, tool filtering, workflow state, and user approval. The Python SDK handles the protocol details. Your job is to build the application behavior around it.