Designing Reliable Tool Schemas with Zod for LLM Agents

LLM agents often fail in surprisingly ordinary places. Not in the model call. Not in the prompt. Not even in the function that eventually does the work. They fail at the boundary between "the model produced some arguments" and "my application trusted those arguments enough to run code." That boundary is where tool schemas matter. If you are building anything agent-like in TypeScript, such as an internal automation, an MCP server, a CLI helper, or a backend workflow that lets a model call functio