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BC
October 3, 2025The three-role architecture (host/client/server) oversimplifies how these components actually interact in production deployments. The clear separation works in theory but falls apart in practice when considering authentication flows, error handling, and state management across multiple servers. I’ve tested similar patterns locally—coordinating multiple tool calls through a central client while maintaining session context quickly becomes complicated, especially when servers have different response times or fail intermittently.
The “capability negotiation” step ignores a key issue: how does the client choose which server to use when multiple servers provide similar capabilities? In reality, this requires either hardcoded priority rules or another LLM call to make the selection, both of which introduce latency and potential failure points. When testing multi-server scenarios locally, I’ve seen models consistently pick the wrong server when descriptions are similar, requiring explicit routing logic that undermines the abstraction.
The security benefit of “access rules managed consistently across servers” is overstated. Each MCP server still uses its own authorization logic, which results in the very inconsistency the protocol claims to prevent.
Without a centralized policy engine—which the article does not mention—you are just standardizing the interface while permissions remain scattered across different implementations.
The database lookup example illustrates the core issue: you build an MCP server to restrict access to “safe queries,” but defining what is safe requires domain expertise and continuous upkeep. Every new query type needs to be vetted and implemented. The abstraction doesn’t eliminate integration work; it simply shifts it from client-side connectors to server-side query handlers.