Startup profile for Stainless: latest funding, latest known valuation, total disclosed funding, investors, status, sources, and why the company is interesting. Part of the Venture Capital Tracker startup directory.
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Stainless funding, valuation and investors

Platform generating and maintaining high-quality SDKs from OpenAPI specs.

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Funding, valuation & investors

Answer-first snapshot

Latest funding

Series A

$25M · December 2024

Latest known valuation

Not publicly disclosed

Total disclosed equity funding

$29M

Excludes debt, grants, acquisitions, secondaries, and IPO proceeds.

Current status

private

series a · San Francisco, California

Investors in latest funding

Lead: Andreessen Horowitz

Other: Sequoia Capital

Sources: latest funding Last verified: 2026-07-25

Overview

Stainless generates production-quality SDKs in multiple languages from OpenAPI specifications, handling pagination, retries, and type safety automatically. Founded by Alex Finkelstein and team, the company serves API-first companies (OpenAI, Cloudflare, Anthropic customers) who need client libraries without maintaining them manually. Sequoia led $3.5M seed in 2022; a16z led $25M Series A in December 2024.

Why Stainless is interesting

Stainless automates SDK craftsmanship — critical as API surfaces and AI tool-calling explode; a16z-led Series A after Sequoia seed.

Product & use cases

Stainless ingests OpenAPI specs and outputs idiomatic SDKs for Python, TypeScript, Go, Java, and more — with docs, tests, and publishing pipelines maintained on spec changes.

  • Auto-generate SDKs for public APIs
  • Keep client libraries synced with API changes
  • Support AI tool-calling with typed client interfaces
  • Reduce SDK maintenance burden for developer platforms

Key facts

  • Series A (Dec 2024): $25M led by a16z — Stainless blog
  • Seed (2022): $3.5M led by Sequoia
  • Customers include major API-first companies
  • SDK codegen from OpenAPI specs

Funding history (newest first)

Series A

2024-12 $25M

Source: https://stainless.com/blog/series-a

Seed

2022 $3.5M

Source: https://www.finsmes.com/2022/08/stainless-raises-3-5m-in-seed-funding.html

Investors in our directory

Funds linked from Stainless's profile — open a fund page for stage focus and related deal articles.

Andreessen Horowitz Sequoia Capital

Competitive landscape

Edge: Opinionated SDK quality beyond openapi-generator — handles edge cases API companies hit at scale.

Every API company needs SDKs; most hate maintaining them. Stainless bets codegen-as-a-service wins as AI agents need typed tool interfaces. a16z + Sequoia signal developer infra conviction.

  • openapi-generator alternative

    Open-source codegen; less polished output and maintenance.

  • Speakeasy direct

    SDK generation competitor for API companies.

  • Manual SDK maintenance alternative

    In-house engineering teams writing clients by hand.

  • Postman API client adjacent

    API testing and client generation features.

Notable stories

  • Stainless founders saw every API company rebuild the same SDK maintenance pipeline — productized what Stripe and others built internally.
  • December 2024 Series A timed with AI agent tool-calling requiring typed API clients at scale.

Industries

Developer Tools AI & Machine Learning Enterprise SaaS

FAQs about Stainless

Practical answers founders, operators, and investors typically search for.

Stainless generates and maintains production-quality SDKs from OpenAPI specifications across multiple programming languages.
Andreessen Horowitz (/fund/andreessen-horowitz) led Series A. Sequoia (/fund/sequoia) led seed and participated in Series A.
Stainless produces higher-quality idiomatic SDKs with ongoing maintenance; openapi-generator is free but requires more manual cleanup.
December 2024 — $25M led by a16z.
API-first companies including developer platforms that need client libraries without large SDK teams.
Typed SDKs give LLM agents reliable interfaces to call APIs — reduces hallucinated parameter errors.
Alex Finkelstein co-founded Stainless.
Commercial product; check stainless.com for pricing and docs.
San Francisco, California.
We track a16z-backed developer tools companies.
Website All startups Funding news

By Venture Capital Tracker

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Editorial note: AI tools assisted with research, structure, or drafting. Venture Capital Tracker retains human editorial responsibility for factual accuracy, relevance, and source quality before publication.