What Stainless does

Stainless is a New York-based developer-infrastructure company that converts a customer's OpenAPI 3.x specification into production-grade, idiomatic client libraries (SDKs) across TypeScript, Python, Go, Java, Kotlin, Ruby, C#, PHP, and Terraform. Its core product is an AI-assisted compiler paired with a stainless.yaml configuration that drives automated regeneration: when a spec changes, Stainless opens pull requests on customer GitHub repositories and publishes new SDK versions directly to npm, PyPI, Maven Central, NuGet, RubyGems, JSR, and the Terraform Registry. The platform extends beyond SDKs with two add-on modules: an Astro-based Docs Platform that keeps API reference documentation, narrative content, and llms.txt output synchronized with the same spec, and a code-mode Model Context Protocol (MCP) server generator that lets AI coding agents search SDK docs and execute typed code against the generated SDK inside an isolated Cloudflare Workers sandbox.

The business is sold on a freemium, product-led motion through a self-serve web app at app.stainless.com, with a parallel enterprise sales motion ([email protected]) for Pro and Enterprise tiers that unlock features such as native Server-Sent Events support, MCP deployment, and air-gapped-style enterprise deployment. Distribution runs through both direct self-serve signups and public package registries, while developer relations and case studies (Cloudflare, OpenAI, Letta, Lithic, Modern Treasury, MUX, Replicate, Turbopuffer, Weights & Biases) carry mid-funnel conversion. Pricing for comparable platforms spans free to roughly $600 per language per month; Stainless discloses a free tier and paid enterprise plans but does not publish list prices. The company reached $5.1M in annual recurring revenue by late 2025 and was acquired by Anthropic on May 18, 2026 in a deal reported at over $300 million, after which the team is being absorbed into Anthropic's Claude Platform organization and all hosted Stainless products are being wound down.

Name

Stainless

Legal name

Stainless Software, Inc.

Website

https://stainless.com

Company type

Private

Founded year

2022

Operating status

Acquired

Headcount range

11–50 employees

Short description

Stainless was a developer-infrastructure company that generated idiomatic, type-safe SDKs, API documentation, and code-mode MCP servers from a customer's OpenAPI spec, serving AI labs (OpenAI, Anthropic, Google, Meta) and infrastructure firms (Cloudflare) before being acquired by Anthropic in May 2026.

Ownership category

akta.pro rank

Headquarters

HQ city

New York

HQ country

United States

HQ region

North America

Offices1 record

Markets served

GTM type

B2B

Offering type

Software

Cost components

Personnel, Technology or R&D, Infrastructure, Marketing or Sales

Revenue model

1. Stainless SaaS ARR: Self-reported $5.1M annual recurring revenue as of late 2025; described as a bootstrapped SaaS business prior to Series A.
2. Free tier / self-service SDK generation: "Free to get started" self-serve plan via app.stainless.com, intended to drive adoption and convert into paid plans.
3. Enterprise plans: Paid enterprise/pro tiers offering advanced features such as native SSE support, MCP deployment, and priority support; sales handled via [email protected].

Pricing tiers

Go-to-market motion4 records

Distribution channels4 records

Marketing channels6 records

Core offering

Stainless is a developer-tooling platform that converts a company's OpenAPI 3.x specification into production-ready, idiomatic, fully-typed client SDKs across multiple programming languages, then auto-publishes them to package managers via GitHub Actions. The platform also includes an Astro-based API reference and documentation module and a code-mode Model Context Protocol (MCP) server generator that lets AI coding agents execute TypeScript against the generated SDK inside isolated Cloudflare Workers sandboxes.

Product overview

Stainless is a single unified developer-tooling platform that turns a company's OpenAPI specification into production-ready developer artifacts. The core product is the Stainless SDK Generator, which is complemented by two platform modules: the Stainless Docs Platform (for auto-synced, AI-searchable API reference docs built on Astro) and Stainless MCP (for code-mode Model Context Protocol servers that let AI agents use the generated SDK directly). Together the three offerings address the full developer-experience stack — SDK distribution, API documentation, and agent connectivity — and all artifacts regenerate automatically from the same OpenAPI source whenever the spec changes. Following the May 18, 2026 acquisition by Anthropic, Stainless has begun winding down its hosted products and integrating the team into the Claude Platform team.

Differentiator

Problem solved

Functional benefit

Products and services

• Stainless SDK Generator Compiler-based product that ingests an OpenAPI 3.x specification and a stainless.yaml config to produce idiomatic, fully-typed client SDKs in TypeScript, Python, Go, Java, Kotlin, Ruby, Terraform, C#, and PHP, with auto-pagination, retries, streaming, webhooks, and file-upload support; SDKs are auto-published to npm, PyPI, Maven Central, NuGet, and RubyGems via GitHub Actions.
• Stainless Docs Platform Astro-based API reference and documentation platform that auto-syncs REST API, SDK, and narrative documentation from the OpenAPI spec; includes AI-powered hybrid search, llms.txt output for AI tools, light/dark themes, custom React/Svelte/Vue/Solid/Preact components, and one-click deployment to Cloudflare-hosted or self-hosted targets.
• Stainless MCP (Code Mode MCP Servers) Generates code-mode Model Context Protocol (MCP) servers directly from the user's OpenAPI spec; each MCP server exposes only two tools (search_docs and execute), letting agents search SDK docs and run TypeScript code against the Stainless-generated SDK inside an isolated Cloudflare Workers sandbox, avoiding context bloat from hundreds of endpoint schemas.

Quantifiable outcome

• Cloudflare went from inconsistent, manually maintained SDKs to automatically shipping over 1,000 endpoints across three language SDKs within a few months
• +3 more outcomes

Named customers13 records

Segments3 records

Ideal customer profiles3 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Integration9 records

AI capability9 records

Feature7 records

Partnerships

Nine partnerships are on record, tiered flagship, core and minor.

• AnthropicflagshipStrategic or Co-development Partner · 18 May 2025Anthropic acquired Stainless on May 18, 2025 in a deal reported at over $300 million. The Stainless team joined Anthropic's Claude Platform team to advance Claude's connectivity capabilities and integrate the SDK generator, MCP servers, and Docs Platform into Anthropic's developer stack. Anthropic has wound down all hosted Stainless products while allowing existing customers to retain ownership of their generated SDKs.
• CloudflareflagshipTechnology or IntegrationCloudflare adopted Stainless as its SDK-generation pipeline after completing its transition to OpenAPI, generating three language SDKs and over 1,000 endpoints automatically. Cloudflare is also featured as a flagship customer case study and provided a public testimonial.
• OpenAIflagshipTechnology or IntegrationOpenAI uses Stainless to generate its official multi-language SDKs for the OpenAI API and is listed as a flagship customer. The Stainless-generated SDKs are published to npm, PyPI, and other registries on OpenAI's behalf.
• GooglecoreTechnology or IntegrationStainless generated the official SDKs for Google Gemini APIs across multiple languages; Google is identified as one of Stainless's largest AI-lab customers prior to the Anthropic acquisition.
• MetacoreTechnology or IntegrationStainless generated the official SDKs for Meta Llama APIs. Meta is referenced as a major AI customer of Stainless's SDK infrastructure.
• GitHubcoreTechnology or IntegrationStainless integrates with GitHub via a GitHub Action that watches a customer's OpenAPI spec and opens pull requests on SDK repositories whenever the spec changes, with deterministic merge-conflict-free updates.
• Stripe, Inc.minorOEM/ Whitelabel/ Licensing PartnerStripe is used as Stainless's third-party payment processor for Paid Services (per the Stainless Self-Service Agreement). The Stripe integration processes all subscription billing for Stainless.
• AstrocoreTechnology or IntegrationThe Stainless Docs Platform is built on the open-source Astro framework; customers extend sites with React, Svelte, Vue, Solid, and Preact components and deploy via Vercel, Fly.io, or Cloudflare.
• Cloudflare (Workers)coreTechnology or IntegrationStainless-generated MCP code-mode servers execute code inside isolated Cloudflare Workers per request; the company also offers one-click deployment to Cloudflare Workers.

Scale indicators7 records

Recent moves6 records

Expansion highlights5 records

Direct peers

• Mintlify: Developer documentation platform with auto-sync from OpenAPI specs, MDX components, and AI-powered search; competes most directly with Stainless's Docs Platform module for API reference and narrative docs.
• APIMatic: API tooling vendor offering automated SDK generation, API docs, and code conversion across multiple languages from OpenAPI/Swagger and other specs — overlapping directly with Stainless's SDK generation use cases.
• Fern: API-first SDK generator and documentation platform that compiles an API definition into typed SDKs and a hosted docs site — closely comparable to Stainless's combined SDK Generator + Docs Platform offering.
• Speakeasy: Commercial SDK generator that turns OpenAPI/AsyncAPI specs into idiomatic, type-safe client libraries across many languages with publish-to-registry workflows — directly competes with Stainless's SDK Generator on the same product category and target buyer.
• liblab: Automated SDK and API documentation generator targeting enterprise developer experience teams; competes head-on with Stainless on multi-language SDK publishing and docs generation.

Broad incumbents

• ReadMe: Established API documentation and developer hub platform with API explorer, metrics, and OpenAPI sync — a broader incumbent that overlaps with Stainless's Docs Platform but does not focus on multi-language SDK generation.
• Anthropic (MCP ecosystem): Creator and primary steward of the Model Context Protocol standard; Stainless's MCP code-mode servers are tightly coupled to MCP's evolution, and Anthropic's acquisition of Stainless makes it both parent and ecosystem-shaping incumbent.
• SwaggerHub: SmartBear's API design, documentation, and (via OpenAPI Generator) SDK tooling suite — overlaps with Stainless on the design-to-SDK pipeline but as part of a much broader API lifecycle portfolio.

Emerging players

• OpenAPI Generator: Open-source, community-maintained SDK generator supporting 50+ languages; the primary free alternative that constrains Stainless's pricing power and forces Stainless to differentiate on output quality and customization.

Others

• Cloudflare Workers / Cloudflare for AI: Edge compute platform used by Stainless to deploy and sandbox MCP code-mode servers; also a flagship Stainless customer — adjacent infrastructure dependency and a channel for Stainless-generated artifacts.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat5 records

Key risks5 records

Key highlights7 records

Customer concentration

• GitHubgithub.com/stainless-sdks
• LinkedInlinkedin.com/company/stainlessapi
• Xx.com/StainlessAPI

Compliance2 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles1 record

Subsidiaries1 record

Funding overview

Funding rounds2 records

Investors6 records

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Stainless