# Fern

**Canonical:** https://apis.io/providers/fern-api/  
**Website:** https://buildwithfern.com  
**APIs profiled:** 5

Fern is a developer-tools platform that turns a single API specification into idiomatic client SDKs, beautiful API documentation, and MCP servers. Given OpenAPI, AsyncAPI, gRPC/Protobuf, or Fern's own Fern Definition as input, Fern generates type-safe SDKs in TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, and Rust, publishes them to registries like npm, PyPI, and Maven, and builds a hosted docs site with an interactive API reference, API playground, and an AI-powered "Ask Fern" search. The primary interface is the open-source `fern` CLI (Apache-2.0, github.com/fern-api/fern) driving a hosted platform - the fern-api catalog documents Fern's SDK-generation, documentation-generation, and Fern Definition capability surfaces as capability areas, plus the one hosted public REST API Fern exposes to customers, the Ask Fern API. Fern is open-core: the CLI and generators are open source, and Docs and SDKs are sold on Hobby (free), Team, and Enterprise plans.

## Kin Score — 35.1 / 100 (thin)

Scored 2026-08-24 under rubric 0.13.0. Trend: flat (-0.3 from 35.4).

| Facet | Score |
|---|---|
| Discoverability | 64.8 |
| Contract Quality | 55.8 |
| Governance | 0.0 |
| Contract Governance | 0.0 |
| Operational Transparency | 34.2 |
| Developer Ergonomics | 23.8 |
| Commercial Clarity | 39.5 |
| Access Clarity | 39.5 |

Regulatory layer — **Education & Research**: 11.1 (matched via tags).

## Agent readiness — 19.8 (agent-aware)

| Dimension | Value |
|---|---|
| Spec Presence | yes |
| Agentic Access | derived |
| Reversibility Documented | no |
| MCP Server | no |
| Auth Clarity | bearer |
| Idempotency | no |
| Error Semantics | no |
| OpenAPI Examples | no |
| Rate Limit Signal | documented |
| Event Surface Described | no |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |
| Delegated Identity | no |
| Protected Resource Metadata | no |
| Dynamic Client Registration | no |
| Agentic Commerce | no |

## Access

Freemium · Self-serve signup — onboarding: self-serve, pricing: freemium, trial: no (confidence: high).

## APIs (5)

- **Fern SDK Generation** — Capability area (CLI/platform, not a hosted REST API) that generates idiomatic, type-safe client SDKs in TypeScript, Python, Go, Java, C#, PHP, Ruby, Swift, and Rust from OpenAP...
- **Fern API Documentation** — Capability area (CLI/platform) that builds a hosted documentation website with a generated API reference, interactive API playground, changelogs, versioning, keyword search, and...
- **Fern Definition and CLI** — Capability area covering Fern's open-source (Apache-2.0) command-line interface and the proprietary Fern Definition API-description format. Core commands include `fern init`, `f...
- **Fern Ask API** — Query indexed documentation for AI-generated, grounded answers.
- **Fern Website Sources API** — Index documentation websites and check indexing job status.

## Agentic access (1)

- **Fern Api Agentic Access** — 3 operations · 1 acting

## Security (1)

- **Fern Api Authentication** — http · 1 scheme

## Plans (1)

- **Fern Api Plans Pricing**

## Tags

API Lifecycle, SDK Generation, Client Library, API Documentation, Developer Tools, OpenAPI, CLI, Open-Source, Developer Experience

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/fern-api/). Scores are computed from the provider's own public artifacts under a published rubric.