name: Fern Vocabulary
description: >-
  Controlled vocabulary describing the concepts, artifacts, products, and integration
  surfaces of the Fern SDK generation and documentation platform. Used to align
  apis.yml, capabilities, JSON Schemas, and JSON-LD across the api-evangelist
  fern repository.
provider: Fern
providerId: fern
version: '0.2'
created: '2026-05-22'
tags:
  - Agent Ready
  - AI
  - API Definitions
  - Code Generation
  - Developer Experience
  - Documentation
  - MCP
  - OpenAPI
  - SDKs
terms:
  - term: Fern Platform
    definition: The hosted Fern offering that ingests API source-of-truth specifications and produces SDKs, docs, CLIs, llms.txt, and an MCP knowledge surface.
  - term: Fern Definition Language
    definition: Fern's purpose-built API description language, used as an alternative to OpenAPI for authoring API contracts.
  - term: API Definition
    definition: A single API surface managed inside a Fern project, sourced from OpenAPI, AsyncAPI, Protobuf, OpenRPC, or the Fern Definition Language.
  - term: SDK Generator
    definition: A Fern component that compiles an API definition into an idiomatic SDK for a specific target language.
  - term: Generated SDK
    definition: A versioned, type-safe client library produced by a Fern SDK generator and published to a language-native package registry.
  - term: Docs Site
    definition: A Fern-managed documentation site rendering navigation, MDX content, API reference, changelog, and AI search from a Fern docs configuration.
  - term: API Reference
    definition: The auto-generated, interactive API reference section of a Fern docs site, including request/response schemas and code samples.
  - term: API Explorer
    definition: The in-docs interactive request playground that lets developers exercise an API directly from the documentation.
  - term: Ask Fern
    definition: Fern's AI-powered in-docs search and chat surface grounded in the customer's docs, SDKs, and guides.
  - term: Fern Writer
    definition: AI-assisted documentation authoring inside the Fern docs platform.
  - term: llms.txt
    definition: Auto-generated machine-readable markdown index of a Fern docs site, designed for LLM and AI agent consumption.
  - term: MCP Server
    definition: Fern's Model Context Protocol server that exposes Ask Fern AI to MCP-aware clients such as Claude Desktop, Claude Code, Cursor, and Windsurf.
  - term: ask_fern_ai
    definition: The primary MCP tool exposed by the fern-mcp-server, accepting a natural-language query against the Fern knowledge base.
  - term: Agent Score
    definition: Fern's open-source tool that rates documentation sites on their agent readiness.
  - term: Agent Readiness
    definition: The degree to which a documentation site can be navigated, parsed, and reasoned about by AI agents, evaluated across structure, semantics, and machine-readable artifacts.
  - term: Generator Configuration
    definition: The YAML or JSON block declaring a generator, its version, output target, and publishing behavior.
  - term: Output Mode
    definition: Whether a generated SDK is written to the local file system, a GitHub repository, or directly to a package registry such as npm or PyPI.
  - term: Source of Truth
    definition: The single API specification artifact (OpenAPI, AsyncAPI, Protobuf, OpenRPC, or Fern Definition) that Fern reads to drive all downstream outputs.
  - term: Multi-Protocol Support
    definition: Fern's ability to model REST, Webhooks, WebSockets, gRPC, and JSON-RPC inside a unified docs and SDK pipeline.
  - term: Visitor Authentication
    definition: Per-visitor JWT or SSO gating of docs content for partner or internal audiences.
  - term: Self-Hosting
    definition: Enterprise deployment of the Fern docs platform inside a customer-controlled environment.
  - term: Migration Checker
    definition: Fern's tooling for comparing legacy documentation sites against a Fern target to catch missing pages and broken links during migration.
  - term: Sync OpenAPI Action
    definition: The fern-api/sync-openapi GitHub Action that pulls a remote OpenAPI specification into a Fern repository on schedule or on demand.