A startup called Fern is on a mission to simplify the maintenance of software development kits and their associated documentation after raising $9 million in an early-stage round of funding today.

The Series A round was led by high profile investors Bessemer Venture Partners and Y Combinator, bringing Fern’s total amount raised to date to $13 million.

Fern, officially incorporated as Birch Solutions Inc., wants to help companies make the lives of third-party developers easier by automating the upkeep of their SDKs, which are necessary to interact with public application programming interfaces.

SDKs are a collection of tools, libraries and instructions that assist developers in building software applications. They consist of various pre-built components and guidelines that outline how to build software that can connect to a given platform or programming environment. Developers consider SDKs to be essential when working with application programming interfaces or APIs, which are the interfaces that connect most modern apps.

Larger enterprises can afford to invest in dedicated teams to ensure the upkeep of their SDKs and the associated documentation, but the reality is that most smaller businesses cannot do this, because doing so requires huge engineering resources. It’s a serious problem because SDK maintenance is essential for APIs, which are updated on a rapid basis. If the API is updated but the SDKs and docs are not, it can cause serious headaches for developers.

That’s what Fern intends to solve, using artificial intelligence to analyze APIs and automatically generate and update SDKs in multiple programming languages, including TypeScript, Python, Go, Java, C#, PHP and Ruby. Its main offering is called the Fern SDK Generator, designed to automate the tedious work of publishing and maintaining SDKs, and then automatically publish them to registries such as GitHub, npm and PyPI.

Besides generating SDKs, Fern also automates the creation of their necessary docs. Fern Docs can be used to quickly create “beautiful and highly customizable documentation websites” with extensive styling options to match any company’s brand. For each docs website it creates, it also publishes an API Reference that provides an overview of the associated API, so developers can quickly understand its purpose and how it works.

Within the API Reference, Fern provides a full-featured playground for developers to begin interacting with the API in an experimental way, so they can understand its various features and functions.

In the near future, Fern will launch a new AI assistant called Ask AI, which will be able to automatically answer technical questions about the documentation it creates.

The startup says this approach, generating and updating both SDKs and their documentation, is the most effective way for companies to ensure a smooth experience for developers interacting with their APIs. That’s because developers expect all of the methods and parameters in the SDK to be fully documented, so they can learn about its capabilities from the comfort of their own integrated development environment. That includes code samples that are always up-to-date, and links to the corresponding docs for complex concepts mentioned in the SDK.

Fern, which launched in 2023, says its offerings are being used by more than 150 enterprises already, including companies like Square Inc., LaunchDarkly, Eleven Labs Inc. and Webflow Inc.

“We used to struggle with keeping our SDKs and Docs in sync,” said ElevenLabs Developer Experience Engineer Paul Asjes. “With Fern, we consolidated both into one streamlined pipeline, ensuring a consistent, high-quality developer experience.”

Though Fern is mainly focused on helping human developers, it says it’s also very aware that AI agents are likely to take on much more work in the coming years, which explains why it’s also future-proofing its tools to take care of them, too. To prepare for this shift, the startup is working on the creation of Model Context Protocol servers that will transform APIs into an agent-accessible interface, supporting autonomous integrations.

Bessemer Venture’s vice president Lindsey Li said the explosion of AI-driven developer tools has resulted in an urgent need for faster, frictionless API integrations, which is exactly what Fern provides.

“By eliminating friction from the developer experience and managing the gritty engineering work that is building and maintaining SDKs and docs, Fern has established itself as a trusted enterprise partner,” Li said.

Image: Fern