MCP Academy · Lesson

Why Schemas Beat Loose Args

Let the model send valid input every time.

Loose Args Are Risky

When a tool takes a plain dict or untyped values, the model can send almost anything, and your code only finds out when it crashes. 😬

A Schema Is a Contract

A schema is a clear contract: it states exactly which fields exist, their types, and which are required before any code runs.

All lessons in this course

  1. Why Schemas Beat Loose Args
  2. Model Inputs with Pydantic
  3. Constraints, Defaults & Enums
  4. Field Descriptions That Guide the Model
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