Fern · JSON Structure

Fern Api Definition Structure

JSON Structure representation of a Fern API definition. Captures the upstream source, target protocols, authentication, environments, and generators a Fern project pulls together.

Type: object Properties: 9 Required: 3
Agent ReadyAIAPI DefinitionsAsyncAPICode GenerationDeveloper ExperienceDeveloper PortalDocumentationgRPCllms.txtMCPOpenAPIOpenRPCPlatformProtobufSDKsWebSockets

FernApiDefinition is a JSON Structure definition published by Fern, describing 9 properties, of which 3 are required. It conforms to the https://json-structure.org/2025/draft/schema meta-schema.

Properties

id name version description source protocols auth environments generators

Meta-schema: https://json-structure.org/2025/draft/schema

JSON Structure

fern-api-definition-structure.json Raw ↑ 
{
  "$schema": "https://json-structure.org/2025/draft/schema",
  "$id": "https://raw.githubusercontent.com/api-evangelist/fern/main/json-structure/fern-api-definition-structure.json",
  "name": "FernApiDefinition",
  "description": "JSON Structure representation of a Fern API definition. Captures the upstream source, target protocols, authentication, environments, and generators a Fern project pulls together.",
  "type": "object",
  "properties": {
    "id": {"type": "string"},
    "name": {"type": "string"},
    "version": {"type": "string"},
    "description": {"type": "string"},
    "source": {
      "type": "object",
      "properties": {
        "type": {"type": "string", "enum": ["openapi", "asyncapi", "protobuf", "openrpc", "fern-definition"]},
        "path": {"type": "string"},
        "url": {"type": "uri"}
      }
    },
    "protocols": {
      "type": "array",
      "items": {"type": "string", "enum": ["rest", "websocket", "grpc", "webhook", "json-rpc"]}
    },
    "auth": {
      "type": "object",
      "properties": {
        "schemes": {
          "type": "array",
          "items": {"type": "string"}
        }
      }
    },
    "environments": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "name": {"type": "string"},
          "url": {"type": "uri"},
          "default": {"type": "boolean"}
        }
      }
    },
    "generators": {
      "type": "array",
      "items": {"$ref": "./fern-sdk-generator-structure.json"}
    }
  },
  "required": ["id", "name", "source"]
}