Stainless is an API developer experience platform that generates best-in-class SDKs, interactive documentation, production-ready CLI tools, MCP servers, and Terraform providers directly from an OpenAPI specification. Trusted by Anthropic, Cloudflare, Google, and OpenAI, Stainless automates the boilerplate of client library development including HTTP requests, retries with exponential backoff, streaming, and pagination. The platform supports TypeScript, Python, Go, Java, Kotlin, Ruby, C#, PHP, and Terraform, with Rust and Swift in development.
Stainless publishes 12 API contracts indexed on the APIs.io network, including Build Target Outputs API, Builds API, Orgs API, and 9 more. Tagged areas include Code Generation, Documentation, Developer Experience, MCP, and Platform.
The Stainless catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.
Stainless’ developer surface includes CLI, support, API reference, getting-started guide, authentication, developer portal, documentation, and 34 more developer resources.
Regulatory Posture applies to this provider. Its tags matched the
Horizontal (data, software, accessibility, platform) regime, so
Regulatory Posture carries 15 points of the composite.
If this regime is wrong for your business, say so on your
provider repo — the
applicability map is public and we will correct it.
Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it
carries 10 points of the composite. It is scored from the published contracts
themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already
holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in
front of it, and the first time that check is skipped a duplicate record is created.
Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet,
not penalised by it.
The six quality facets above are damped to 75 points between them,
because the conditional facet above carries the other
25. That is why each facet's contribution is shown against a damped
maximum: raising a quality facet moves the composite by 75% of its nominal
weight, not 100%. The full arithmetic is at apis.io/rating/.
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Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/stainless: open an issue to ask a question, or submit a pull request to add artifacts.
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Stainless is an area vendor: providers adopt it to run part of their developer surface. This is the Kin Score checks its features can move for a provider that adopts it, what each one really earns, and what it earns nothing for.
sdk generationcapability map9 features checked 2026-09-25 · rubric v0.22.0
Stainless reaches the most Developer Ergonomics surface of the SDK generators: SDKs in eight or more languages, a generated CLI, and a static, server-light docs platform with an API reference, per-page Markdown and an llms.txt. Each counts once the provider declares it. Its MCP servers expose the same two Code Mode tools for every customer, so they score as platform (0.25 of 12). Its generated SKILL.md files are the derived class (0.25). The decorated OpenAPI adds SDK snippets, not request/response examples, and is not an Overlay document, so neither examples_present nor overlay_published moves. Unless the provider uses the docs platform or a default-hosted MCP server, Stainless output looks like the provider’s own work.
Agent Readiness6.0 of 139 pts
Contract Quality4.0 of 211 pts
Developer Ergonomics17.8 of 42 pts
Discoverability4.0 of 54 pts
Check
Earns
Through
MCP Serverplatform Agent ReadinessCode Mode exposes the same two tools (docs search, execute code) for every Stainless customer. That shared tool shape is what 0.22.0 grades platform (0.25). There is a fair argument that the SDK behind the executor is the provider’s own. It belongs in the…
Request/Response Examplespartial Agent ReadinessThe added snippets are SDK calls, not request/response examples. The dimension reads examples first, so Stainless reaches only the Code Samples link fallback (0.25).
Documentationsaturated Developer Ergonomics95% of providers with a contract, docs and a reference already earn this; the vendor cannot move it for most of its buyers.
API referencesaturated Developer Ergonomics94% of providers with a contract, docs and a reference already earn this; the vendor cannot move it for most of its buyers.
Across 8977 providers that publish a contract, adopting Stainless would move 8961. Median lift: composite +6.4 (90th percentile +8.1), agent readiness +3.1 (+4.3). Conditional rows excluded.
What Stainless ships that earns nothing (4)
Decorated OpenAPI with SDK code samples — x-codeSamples and x-stainless-snippets are SDK snippets. The check counts request or response examples.
Decorated OpenAPI with SDK code samples — The decorated spec is a full copy of the OpenAPI with snippets added, not an OpenAPI Overlay document.
Stainless CLI skill (stl skills) — The stl skill teaches an agent to drive Stainless and says nothing about the customer’s API.
SDK generation — SDK retries do not add an idempotency key to the contract, and the dimension reads the contract.
A model, not a score. Adopting this vendor changes a provider's Kin Score only when the provider publishes the resulting artifacts on its own surface; nothing here writes a score, and no sponsorship or partnership can. The rating is not for sale → · Full vendor facets artifact
Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.
The Stainless Docs Platform combines your API reference, usage examples, and narrative guides into a single, cohesive experience that evolves with your API. Go from an OpenAPI s...
The Stainless CLI generates production-ready command-line interfaces from an OpenAPI specification. Generated CLIs provide a consistent, typed interface for interacting with any...
Stainless generates production-ready Terraform providers from an OpenAPI specification, enabling infrastructure-as-code access to any REST API without manual Terraform provider ...
Overlays applied on top of this provider's contracts. Each card says who wrote it: a document the provider publishes, or one API Evangelist derived or generated.
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