Client SDKs from
your OpenAPI spec
in minutes, not months
Upload or paste your spec, download a typed SDK ZIP, and integrate on your servers — no Ferrumlabs runtime required. Skip hiring a dev to hand-write clients from scratch.
Free: 10 generations/month to prove your spec. Pro ($99/mo): unlimited generation across all 7 languages — fast iteration when you are ready to ship.
import { PetstoreClient } from 'petstore-sdk';
const client = new PetstoreClient({
apiKey: process.env.PETSTORE_API_KEY,
});
// Sub-resource nesting — like Stainless
const pets = await client.pet.findByStatus('available');
const order = await client.store.placeOrder({ petId: 1, quantity: 2 });
const user = await client.user.getByName('john');Ship an SDK in three steps
No config files. No YAML schemas. Just your spec.
Paste or upload your spec
Drop in a JSON or YAML OpenAPI spec, fetch from a URL, or upload a file. We handle both OpenAPI 3.0 and 3.1.
Pick your language
Choose from 7 languages: TypeScript, Python, Go, Java, C# / .NET, PHP, and Ruby. Each SDK follows the idioms of its ecosystem.
Download & test on your stack
Unzip, wire auth, run against your staging or production API. You own the code — publish to npm, PyPI, Maven, or use it internally.
Try free. Ship faster with Pro.
Generation is the product — download SDKs and validate on your infrastructure. Pay when you need unlimited runs across every language.
Free
$0
10 SDK generations per month. One language per build. Enough to prove your OpenAPI spec works before you commit.
Start freePro
$99/mo
Unlimited generations · all 7 languages · instant ZIP download. Replace weeks of hand-written client code — iterate the same spec in Go, TypeScript, Java, and more.
See Pro detailsPro Verify
$199/mo
Everything in Pro, plus Docker compile checks, Prism mock tests, and TypeScript MCP server generation in our pipeline — optional confidence before you ship.
Validation & MCPBeta pricing · Specs stay private · Not every public OpenAPI on the internet passes — your spec is what matters
Built to integrate, not to demo
Deterministic templates, idiomatic per language — a strong starting point you finish on your own CI and servers.
Zero lock-in, ever
You own every file. Standard package formats, idiomatic code — publishable to npm, PyPI, crates.io, Maven, or any registry. No dependency on us to run.
Sub-resource nesting
Stainless-style architecture. client.projects.tasks.create() instead of flat method lists.
Auth auto-detected
Reads your OpenAPI security schemes. API key headers, Bearer tokens, and OAuth flows are wired up automatically.
Ready to publish
Includes package.json, pom.xml, Cargo.toml — ready for any package registry.
JSON & YAML
Paste, upload a file, or fetch from a URL. Auto-detects format. Works with any public or internal OpenAPI endpoint.
Runs in the background
Submit your spec, close the tab, come back when it's done. Watch live in the build log if you want to — your SDKs build either way.
Model Context Protocol (MCP) Server Generation
FeaturedOn Pro Verify, TypeScript builds can include an MCP server wrapper so agents (Claude Desktop, Cursor, Copilot) can call your API as tools. Pro ($99) is unlimited SDK download — validation and MCP run in our cluster when you need that extra layer.
Your OpenAPI spec is all you need
Stainless does great work — but it requires a hand-crafted .stainless.yml, a sales call, and an enterprise contract. If you already have an OpenAPI spec, you can get the same sub-resource nesting and production quality here — self-serve, in under a minute.
No config file required
We read your OpenAPI spec directly — no .stainless.yml or extra schema layer.
Same sub-resource nesting
client.projects.tasks.create() — the pattern you already know.
Self-serve free tier
No sales call. No waitlist. Sign in and generate your first SDK now.
7 languages, one spec
TypeScript, Python, Go, Java, C#, PHP, and Ruby — regenerate the same spec per language; Pro unlocks unlimited runs.
The developer tools lab
FerrumSDK is live. FerrumApp is next.
Ferrum SDK Builder
Generate production-ready SDKs in 7 languages from any OpenAPI spec. Self-serve, instant, and idiomatic.
Try it nowFerrumApp
Full-stack app scaffolding from a prompt. Generate a production FastAPI + React app with authentication, database, and CI/CD — in minutes.
ferrumapp.devTry your spec free today
10 generations/month on the house — download and test on your servers. Need every language, unlimited? Pro is $99/mo.
7 languages · You own the code · No lock-in