Type Crafter

TypeCrafter is a CLI tool for generating types from a YAML types specification for any language. The tool is heavily inspired by OpenAPI Generator and aims to provide similar functionality for generating types with a simple YAML specification & more flexibility.

Installation

npm i -g type-crafter

Usage

type-crafter generate <language> <types-specification-file> <output-directory>

Example

type-crafter generate typescript types.yaml ./types

Example input specification file can be found here

Input Specification

The input specification is a YAML file that contains the types specification. Refer the following sample specification for the structure:

info:
  version: 0.0.0
  title: Title of your specification
types:
  SampleType:
    type: object
    properties:
      name:
        type: string
groupedTypes:
  SampleGroupedType:
    type: object
    properties:
      name:
        type: string

The input specification yaml file must be of following syntax:

• info - The information about the specification. Specifying the version and title of your spec. This is required.
• types - These are types that will be generated in flat structure.
• groupedTypes - These are types that will be generated and grouped in a folder.

Note: Passing types or groupedTypes is up to your expected results. A valid spec file can contain either types or groupedTypes or both.

The syntax for writing different types can be referred from the OpenAPI Data Types Guide.

Supported Languages

• [✔️] TypeScript
• [✔️] TypeScript with Decoders (runtime validation)
• More languages coming soon

MCP Server (AI Assistant Integration)

Type Crafter includes an MCP (Model Context Protocol) server that helps AI assistants write correct YAML specifications.

Installation

npm install -g @type-crafter/mcp-server

Configuration (Claude Desktop)

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "type-crafter": {
      "command": "type-crafter-mcp"
    }
  }
}

Available Tools

Tool	Description
get-writing-guide	Learn YAML spec format (call first)
get-rules-section	Deep-dive into specific topics
validate-spec	Check specs for errors
get-spec-info	View types in existing spec
list-languages	Show supported languages

Key Features

• Session-based workflow - Guides LLMs to read documentation first
• Educational errors - Explains what's wrong and how to fix it
• Common mistake detection - Catches nullable: true, optional: true, wrong paths

See mcp/README.md for full documentation.

Contributing & Extending

Adding support for a new language

TypeCrafter uses Handlebars to template syntax for different languages.

To add support for a new language, you need to create a new folder in src/templates directory. The folder name will be the name of the language. The folder must implement following files:

• index.ts - The main file that will be exporting the generator config.
• object-syntax.hbs - This Handlebars template file that will be used to generate the object syntax.
• type-file-syntax.hbs - This Handlebars template file that will be used to generate the syntax for file which contains the generated types & its imports.
• exporter-module-syntax.hbs - This Handlebars template file that will be used to generate the syntax for the module that exports the generated types.

Development

To start developing type-crafter, you need to run following commands:

pnpm i
pnpm run dev