JTC (JSON/YAML Type Checker)

JTC validates json, jsonc, and yaml documents against TypeScript types using a $type field.

How It Works

1. Write $type in your document (example: "./types.ts#MyType").
2. JTC parses the document into an internal rough JSON structure.
3. JTC runs TypeScript diagnostics for that value against the target type.
4. Diagnostics are shown directly in VS Code.

$type itself is treated as metadata and excluded from type checking.

Example

{
  "$type": "./types.ts#User",
  "name": "Alice",
  "age": 20
}

./types.ts

export interface User {
  name: string;
  age: number;
}

If a value has the wrong type, JTC reports a diagnostic at the corresponding JSON/YAML path.