MCP Dev Summit North America

Effective context engineering via MCP servers requires understanding how host agents weave the server's responses into their context as conversations unfold.

Context flows through more channels than tool definitions alone: initial instructions, the tool set itself (explicit tools vs. generic execution tools), tool names and parameters, descriptions, response content, structure and length, error feedback, "skill-loading" tools, resources, and sub-agent delegation.

Each mechanism involves trade-offs. Eager loading of context risks bloat; lazy loading adds tool calls. Rich tool responses help agents self-correct but consume tokens. Sub-agents compartmentalize complexity, but limited client support for elicitation creates friction.

Getting this balance right means staying conscious of how much context you're injecting, when, and at what cost (e.g. in # of tool calls to achieve a goal)—a balancing act that's hard without a clear picture of what's happening inside the host agent's context window.

This talk aims at providing a framework for thinking about these decisions—grounded in concrete examples from building the MotherDuck MCP Server.