sdk-gen
paste OpenAPI, get TS/Python/Go SDK ZIP in 1.5s
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What is sdk-gen?
sdk-gen is a free SDK code generator that serves as a replacement for Stainless, which was shut down after Anthropic acquired it. The tool allows users to paste an API specification and immediately download a ZIP file containing generated client SDKs, with no account required. It was built in just 24 hours as a simple, straightforward alternative for developers who previously relied on Stainless.
The tool generates SDKs in three programming languages: TypeScript, Python, and Go. Users simply paste their API spec and receive a downloadable ZIP file containing the generated code. It supports both public specs (free tier) and private spec handling (paid Pack tier). For more advanced needs like watched-repo mode, MCP server output, or custom branding, users can contact the developer directly.
sdk-gen is primarily for developers and companies who had their SDKs generated by Stainless and need a replacement before their September deadline. This includes OpenAI, Google, and hundreds of small startups that were affected by Stainless shutting down. The tool is ideal for teams needing quick SDK generation without the overhead of accounts or complex setup.
sdk-gen pricing
Pricing model: Freemium
Free tier: $0 - Paste spec and download ZIP, supports TS/Python/Go, public spec only. Pack plan: $30 one-time - Includes 5-language SDK pack, private spec handling, and 30-day email support. Watched repo plan: $30/month - Features GitHub spec watch and auto-PR on spec change (currently on waitlist). v1 is free, pricing coming soon for advanced features.
sdk-gen pros
- No account required to use
- Generates SDKs in 3 languages (TS, Python, Go)
- Paste spec and download ZIP instantly
- Free tier available at $0
- Built as direct Stainless replacement
- Simple 24-hour built solution
- Public spec generation completely free
- 30-day email support with Pack plan
- 5-language SDK pack available
- Private spec handling in paid tier
- GitHub spec watch in watched repo plan
- Auto-PR on spec change feature
- First 5 customers get hand-tuned pack free
- JSON paste works directly without conversion
- Open source alternative to proprietary Stainless
sdk-gen cons
- Complex schema features fall back to dict/map
- Python and Go less idiomatic than Stainless
- No auth helpers wired automatically
- Vercel serverless 60s timeout limit
- Very large specs over 500 operations may timeout
- YAML specs require URL paste not raw YAML
- allOf composition not fully supported
- Discriminated unions fall back to generic types
- Recursive refs not fully handled
- Template-based code needs manual refinement
Frequently asked questions about sdk-gen
What is sdk-gen?
sdk-gen is a simple SDK code generator that serves as a replacement for Stainless. You paste your API specification and get a ZIP file with generated client SDKs in TypeScript, Python, and Go. No account is required.
Why does sdk-gen exist?
Anthropic acquired Stainless and shut it down. OpenAI, Google, and hundreds of startups had their SDKs generated by Stainless and needed a replacement before their September deadline. sdk-gen was built in 24 hours as the simplest possible alternative.
Do I need to create an account?
No, sdk-gen requires no account. You can paste your spec and download the ZIP file immediately without signing up or logging in.
What languages does sdk-gen support?
The free tier supports TypeScript, Python, and Go. The paid Pack plan ($30 one-time) includes a 5-language SDK pack for additional languages.
Can I use sdk-gen with private API specs?
Private spec handling is available in the paid Pack plan for $30 one-time. The free tier only supports public specs.
What format should I use for my API spec?
JSON specs can be pasted directly. For YAML specs, you need to paste the URL to the YAML file rather than pasting raw YAML content.
Are there size limits for API specs?
Yes, Vercel's serverless function has a 60-second timeout. Very large specs with over 500 operations may time out and fail to generate.
Does sdk-gen automatically handle authentication?
No, auth helpers are not wired automatically. You need to read the spec's securitySchemes and pass headers via the client constructor manually.
What advanced features are available?
For watched-repo mode (GitHub spec watch with auto-PR), MCP server output, and custom branding, email [email protected]. The first 5 customers get a hand-tuned pack for free.
How does sdk-gen handle complex schema features?
Complex schema features like allOf composition, discriminated unions, and recursive references fall back to dict in Python or map[string]interface{} in Go. The generated code for Python and Go is template-based and may need manual refinement to be more idiomatic.