JSON Schema

In depth

A declarative vocabulary for describing the shape of JSON data: which properties exist, their types, which are required, and what values are allowed. The current version is 2020-12, split into a Core spec that defines the foundation and a Validation spec that defines keywords like type, enum, and required. In AI development it is how tool parameters, MCP tool inputs, and structured output formats are defined, and libraries like Zod can generate it from TypeScript types. Most providers support only a subset of the full spec for constrained output, so check their documented limitations.

Primary source: json-schema.org