MCP Microservices Architecture: Design Patterns

A single monolithic MCP server exposing 80 tools overwhelms the model's context and makes tool selection unreliable. Splitting by domain — one server per bounded context — is the pattern most teams converge on.

Splitting by Domain, Not by Technology

Group tools around a business capability (billing, inventory, support) rather than a data store. This keeps each server's tool list short enough for the model to reason about reliably.

Shared Auth, Independent Deploys

Centralize authentication (a shared OAuth gateway or API key broker) while letting each MCP microservice deploy and scale independently. This mirrors standard microservice practice, with the MCP client acting as the orchestrating caller instead of a browser.

Cross-Server Tool Calls

MCP has no native service-to-service call — composition happens in the client or the model's plan. Keep tools self-contained so a single task rarely needs more than two servers.