Building Multi-Server MCP Architecture

A truly capable AI agent often needs to master more than a single skill. As we expand our agent’s abilities, we encounter a fundamental architectural choice: should we add new skills to our existing tool server, creating a monolithic application, or should we treat each skill as a distinct, composable module? This lesson explores the power of the latter approach, demonstrating how to build a scalable, multi-server agent architecture with MCP.

Scaling our agents’ skills

A single-purpose AI agent, like a weather assistant, is a great starting point. However, the true power of agentic AI is unlocked when a single assistant can perform a wide range of diverse tasks. Imagine wanting our assistant to not only fetch the weather but also check our calendar for availability, query a customer database for recent orders, and then draft an email summarizing the findings. This immediately raises a critical architectural question: how do we best structure our system to accommodate these new, unrelated skills?

The most direct approach might be to build a single, monolithic server that houses every tool the agent could possibly need. However, this all-in-one server quickly becomes a complex, tightly-coupled system. In a real-world enterprise system, this would mean a single codebase trying to manage connections and dependencies for a weather API, a Salesforce database, a Git repository, and a calendar service simultaneously. This monolithic design makes the system difficult to maintain, test, and scale, as a change to one tool integration risks breaking another.

Why a multi-server architecture?

The solution to the monolithic challenge is to adopt a multi-server architecture, a pattern that mirrors the philosophy of microservices in modern software engineering. Instead of creating a single, all-encompassing server, we treat each distinct capability as its own independent micro-tool server. This approach provides several powerful advantages for building robust and scalable agentic systems.

The primary benefits of a multi-server approach include:

• Modularity: Each server handles one specific job, making it significantly easier to develop, test, and debug in isolation. If the customer database integration has a bug, we know to look only in the database_server, leaving the calendar functionality untouched.

• Reusability: By decoupling skills into independent servers, we create ...