API ReferencesGeneration

Generate REST API Reference

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Fern generates REST API Reference documentation from an OpenAPI specification. Once the API definition is set up, adding it to the docs takes just one line of configuration.

Fern also supports gRPC, WebSocket, OpenRPC, and Webhook references.

Configuration

1

Set up your project structure

Add your specification file to your /fern directory and create a generators.yml that references it in the api.specs section:

generators.yml
1api:

2  specs:

3    - openapi: "./openapi.yml"
2

Add the API Reference to your navigation

Add - api: API Reference to your navigation in docs.yml:

docs.yml
1navigation:

2  - api: API Reference

Fern will automatically populate your endpoints, types, and code snippets from your API definition. Request and response examples are generated using AI to show realistic data instead of placeholder values.

3

Customize the layout

For a full list of configuration options and layout customizations, see Customize API Reference layout.

Include more than one API Reference

To include multiple, distinct API definitions in your documentation, use the api-name property. The api-name corresponds to the folder name containing your API definition. For example:

fern
fern.config.json
docs.yml
plant-api
openapi.yml# OpenAPI spec
generators.yml# References the OpenAPI spec
garden-api
openapi.yml# OpenAPI spec
generators.yml# References the OpenAPI spec

For a simple setup without tabs, you can include multiple API References directly in your navigation:

docs.yml
1navigation:

2  - api: Plant Store

3    api-name: plant-api   # Matches folder name containing your API definition

4  - api: Garden

5    api-name: garden-api  # Matches folder name containing your API definition