AI Engineer World's Fair 2026 — unofficial import demo

A dangerous pattern is evolving in the ecosystem: developers are deploying "Build-Time" tools into "Run-Time" environments. In this session, we will introduce a critical distinction for the MCP ecosystem: the difference between Build-Time Agents (Developer Assistants like Gemini Code Assist) and Run-Time Agents (End-user applications like a Customer Support bot). Drawing from our experience building the MCP Toolbox, we will demonstrate why the "Atomic" tools that make Build-Time agents powerful become catastrophic liabilities for Run-Time agents. We will provide a framework for transitioning your architecture across three key axes: Design: Moving from flexible, atomic primitives to "Composite Workflows" that encapsulate business logic. Security: Shifting from "Developer Identity" (trusted) to "Workload Identity" (zero-trust), where the agent is treated as an untrusted user. Reliability: Why production agents need "Agent-Readable" errors (natural language guidance) rather than the stack traces that developers rely on. Attendees will leave with a clear rubric for evaluating whether their tools are truly "Production Ready" or just "Prototype Ready."