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

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.

{
  "$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.

• json-type-checker: core library (@disjukr/jtc)
• jtc-cli: CLI (jtc)
• jtc-vscode: VS Code extension

Prerequisites:

• Deno
• VS Code (or compatible)

Build extension bundle:

cd jtc-vscode
deno task build

Watch mode:

cd jtc-vscode
deno task watch

Run extension dev host:

• Use the Extension launch configuration from .vscode/launch.json.

Install CLI globally:

cd jtc-cli
deno task install-cli

Use CLI:

jtc --help