Generating an SDK

Install the Fern CLI

$
npm install -g fern-api

Initialize the fern folder

Initialize the fern folder with your existing OpenAPI specification. Specify your organization name using the --organization flag.

$
fern init --openapi path/to/openapi.yml \
>
--organization <YourOrganization>

This creates a fern folder in your current directory.

Validate your API definition

Check that your API definition is valid, and fix errors before proceeding:

$
fern check

Add the SDK generator

Run the following command to add the TypeScript SDK generator to generators.yml:

$
fern add fern-typescript-sdk --group {{GROUP_NAME}}

This command adds the following group to generators.yml:

1
  ts-sdk: # group name
2
    generators:
3
      - name: fernapi/fern-typescript-sdk
4
        version: 3.69.0
5
        output:
6
          location: local-file-system
7
          path: ../sdks/typescript

Generate the SDK

Run the following command to generate your SDK:

$
fern generate --group ts-sdk

$
fern generate --group ts-sdk --api your-api-name

This creates a sdks folder in your current directory. The resulting folder structure looks like this:

Set up GitHub repositories

Fern uses a multi-repo structure: your source repository contains the fern/ folder, and each SDK gets its own separate repository.

1. Create a source repository for your fern/ folder if you don’t have one already (e.g., your-org/your-api-definitions).
2. Create an SDK repository for your SDK (e.g., your-org/your-api-typescript-sdk).
3. Install the Fern GitHub App on both repositories.

Publish to npm

Follow the Publishing to npm guide to configure your package and set up automated publishing via GitHub Actions.