Descriptions:
Jeremiah Lowin, founder and CEO of Prefect Technologies and creator of fastmcp, delivers a frank diagnosis of why most MCP servers are poorly designed and what to do about it. With fastmcp downloaded approximately 1.5 million times per day and positioned as the de facto high-level interface for building MCP servers—a status endorsed by Anthropic’s David Hershey, who incorporated an early version into the official SDK—Lowin has unparalleled visibility into real-world MCP server patterns and their failure modes.
The core argument is that MCP server design should borrow directly from human interface design: agents are not oracles, they have known strengths and failure modes, and tool interfaces should be built to accommodate those properties. Specific guidance includes using literals and enums instead of free-form strings for constrained parameters, documenting servers and individual tools thoroughly, and treating examples with care—Lowin demonstrates that examples act as implicit contracts that agents follow with surprising rigidity, often producing exactly the number of items shown in an example regardless of what is actually needed.
Lowin also announces that fastmcp will be formally decoupled from the official Anthropic SDK within months, clarifying its role as a high-level abstraction layer while the SDK focuses on low-level primitives. The talk is particularly valuable for developers building production MCP servers or agentic products that expose tool interfaces, offering a principled framework for thinking about agent ergonomics that goes well beyond API documentation.
📺 Source: AI Engineer · Published January 12, 2026
🏷️ Format: Deep Dive
