Anthropic acquires Stainless to boost Claude integrations

Anthropic has acquired Stainless, a long-time partner behind its software development kits.

Founded in 2022, Stainless has produced every official Anthropic SDK since the early days of the Claude API. Its tools turn an API specification into SDKs, command-line tools and MCP servers that developers and software agents use to connect with external systems.

The acquisition underscores Anthropic's focus on expanding how its Claude platform connects to data sources and software tools. Hundreds of companies have used Stainless to generate SDKs and related tooling in languages including TypeScript, Python, Go, Java and Kotlin.

The move comes as AI companies push beyond chat-style systems toward agents that can take actions across other software environments. In that model, the quality and breadth of integrations become a central part of the product.

Existing relationship

The companies already had close ties before the acquisition. Stainless helped shape the developer experience around the Claude API from the outset and worked on nearly every Claude API launch.

That history featured prominently in comments from both sides. "Stainless has shaped how developers experience the Claude API since the start, and it's been great to work with them on that," said Katelyn Lesse, head of platform engineering at Anthropic.

She added: "Agents are only as useful as what they can connect to. We're excited to bring the Stainless team into Anthropic to advance Claude's ability to connect to data and tools."

The deal also strengthens Anthropic's work around MCP, the protocol it created to support connections between AI agents and external tools. Combining the teams is expected to support further work on developer experience and agent connectivity within the Claude platform.

Product wind-down

As it joins Anthropic, Stainless will wind down its hosted products. That includes its SDK generator, with new sign-ups, projects and SDKs no longer available.

The change affects existing customers that used Stainless-managed products to create and maintain developer tooling around their APIs. Customers will retain ownership of the SDKs they have already generated, along with full rights to modify and extend them.

Alex Rattray, founder and chief executive of Stainless, said the company's work would continue inside Anthropic's platform organisation. "I started Stainless because SDKs deserve as much care as the APIs they wrap. Anthropic was one of the first teams to bet on this with us," he said.

He added: "We have been watching what developers have built on Claude over the last few years, which made bringing our teams together an easy decision. The team gets to keep doing the work we love, on the platform where it matters most."

In a separate message to customers and users, Rattray said Stainless had decided to shut down its hosted offerings as it shifted its efforts to Claude platform work and links between agents and APIs.

Developer footprint

Stainless built its business around the idea that API tooling should be treated as a core part of software design rather than an afterthought. Its software generates language-specific SDKs designed to match the conventions developers expect in each programming language, helping software providers distribute and maintain API access tools at scale.

The company said its tools had reached a significant share of the software industry through customer documentation sites and generated SDKs. Rattray said Stainless estimates that about a quarter of the world's professional software developers have used an SDK or visited a documentation site created with its technology.

That footprint helps explain why the acquisition matters beyond a narrow infrastructure deal. As AI model providers work to make agents more useful in business settings, the systems that connect models to internal software, third-party applications and structured data are becoming more important.

Anthropic has been building its position in that part of the market through Claude and MCP, while rivals across the AI sector are also investing in tools that let models carry out tasks across broader software environments. Bringing Stainless in-house gives Anthropic direct control over a layer of tooling many developers first encounter when integrating with an API.

Rattray described the combination as a continuation of Stainless's original focus on the quality of developer interfaces. "We'll continue to represent those values as we join the Claude Platform team, and we hope you'll be there to push and inspire us along the way," he said.