MCP Servers

A model’s training data is frozen and months stale. MCP servers are how you hand the agent current knowledge and real tools. They’re the “arms and appendages” it didn’t ship with.

Instructor demo: adding CDK the right way

This is a watch-along, not a hands-on (MCP needs network access and is blocked at many companies). Here’s the vignette. We’re about to add infrastructure to the app with AWS CDK. Ask the agent cold and it writes CDK from year-old memory, with wrong constructs and deprecated APIs. Then wire in an AWS docs MCP server and ask again: now it pulls current CDK docs and gets it right. “If we’re going to add CDK, we’d better do it right.”

Caution

Vet any MCP server before connecting it. Review what tools and permissions it exposes. Supply-chain risk is real, and many teams disallow MCP entirely, which is a reasonable stance.

MCP lives on an agent

An MCP server is configured on an agent (the mcpServers field from Custom Agents), so the natural pattern is a scoped agent for risky work: it can run the infra commands and reach the docs MCP, but can’t touch your app source. Least privilege plus fresh knowledge, together.