SDK generator comparisons

Speakeasy and Voxgig, compared

A commercial generator with a Terraform provider target, an MCP server target, and per-language subscription pricing.

Published by Voxgig, which makes one of the two tools compared here. Facts checked against the first-party sources linked below. Corrections go to info@voxgig.com. The scope and method for every page in this section are published.

What Speakeasy is#

Speakeasy is a commercial SDK generation company. You run a single standalone CLI binary locally or in CI, authenticated against a workspace, and it produces SDKs into repositories you own. The generator itself is closed source. The code it writes is yours.

The targets are roughly ten: TypeScript, Python, Go, Java, C#, PHP, Ruby, Kotlin, Unity, and Terraform. Alongside the SDKs it generates MCP servers, documentation, code samples and test suites.

Its design position is that OpenAPI is the source of truth and there should be no second definition format. Where the spec is not shaped the way you want the SDK shaped, you write an OpenAPI Overlay, which is an OpenAPI Initiative specification for a document of targeted edits applied over another document. Generation settings live in a gen.yaml, the pipeline in a workflow.yaml, and the usual deployment is a GitHub Action that regenerates and opens a pull request when the spec changes.

Pricing is a free tier covering a single SDK with a cap on endpoints, then paid plans priced per language per month, then quoted enterprise agreements. Figures move, so the current numbers are on Speakeasy's own pricing page.

What Speakeasy does that Voxgig does not#

Capabilities Speakeasy has that Voxgig does not, in enough detail to evaluate them.

Terraform provider generation

This is the headline, and it deserves to be. If your API provisions anything, your larger customers want a Terraform provider, and hand-writing one is a specialised job most API teams have nobody for: resource and data-source schemas, plan and apply semantics, import, state upgrades, drift. Speakeasy generates one from the same description as the SDK. Voxgig does not generate a provider at all. If you need one, this is a complete reason to choose Speakeasy and nothing on this page argues with it.

OpenAPI Overlays instead of a private config format

Most tools solve the my spec does not describe the library I want problem with a proprietary config file. Speakeasy uses Overlay, which is a published OpenAPI Initiative specification. The practical difference is that your customizations are a standard document other tools can read, and they stay useful if you leave. It is the better-behaved answer to that problem, and it is worth understanding even if you never buy the product.

Runtime validation in the TypeScript SDKs

Their TypeScript output validates responses at runtime with Zod rather than casting the JSON and hoping. When a server returns a field the spec did not promise, or omits one it did, you get an error at the boundary instead of a missing value three frames away. That is a real correctness difference in the language where most people notice it, and it costs a runtime dependency, which is the trade they have chosen to make.

One standalone binary

The CLI ships as a single binary rather than a Node or JVM dependency chain, which makes it usable in locked-down and air-gapped build environments in a way that most Node-based tooling, Voxgig included, is not without work.

The public OpenAPI writing

Their documentation on OpenAPI itself, linting rules, spec hygiene, the parts of the specification that generators actually choke on, is a genuine public good, widely cited, and useful whether or not you ever pay them. It is not a product feature, and it is a common route by which teams find the tool.

Side by side#

No partial ticks and no asterisks. If a tool has a feature, the table says it has it. Where a row would need a paragraph to be true, it is a paragraph somewhere else on this page instead of a row here.

SpeakeasyVoxgig
LicenceGenerator closed source. Generated SDKs are yoursGenerator MIT. Generated SDKs are yours
CostFree tier for one SDK with an endpoint cap, then per language per monthFree
Account neededYesNo
Language targetsAbout 10, including Unity22 bundled language targets, more from packages
Terraform providerYesNo
MCP serverYesYes
CLI and REPL over your APINoYes
CustomizationOpenAPI Overlays, `gen.yaml`, custom code regionsModel, templates, components, features, targets, packages, all in your repo
SupportCommercial, with an SLA on paid plansCommunity, or a paid API Experience engagement

Which one to choose#

Choose Speakeasy when

  • You need a Terraform provider. Nothing else on this page makes the decision as quickly.
  • You want a vendor: a support contract, a roadmap, and somebody to escalate to at two in the morning.
  • You want runtime response validation in TypeScript without building it yourself.
  • You want your spec customizations in a standards-track format rather than a vendor's config file.
  • Your team would rather pay a subscription than own a generator. That is a legitimate answer and often the cheaper one once you price your own time.

Choose Voxgig when

  • You do not want the generator to be a dependency you cannot read, fork, or run after a contract ends.
  • You want many languages. Per-language monthly pricing is the wrong shape for a small team shipping seven SDKs, and the right shape for a large team shipping two.
  • You want the CLI, the REPL and the Agent Skills surfaces as well as the SDK and the MCP server.
  • You need to generate with no account and no network, as a normal condition rather than as an enterprise exception.

Limits of this comparison#

  • Prices and tier limits change often, so this page describes the shape of the pricing rather than printing figures that will be stale in six months.
  • Speakeasy's generator has not been run against a large specification alongside Voxgig's and the output diffed. Nothing on this page is a quality benchmark, in either direction.
  • Speakeasy publishes its own comparison of this field, linked below. It is well researched, and like this page it is published by a vendor in the field.

Corrections go to info@voxgig.com or an issue. A correction changes the page and moves its checked date; corrections from Speakeasy's own team carry the most weight.

Speakeasy documentation#

First-party sources for the claims on this page. Where they disagree with it, they are the authority.

speakeasy.comSpeakeasy pricingSpeakeasy's own comparison of this fieldThe OpenAPI Overlay specification

The other comparisons#

  • OpenAPI GeneratorThe community generator most APIs have shipped an SDK from at least once.
  • FernSDKs and a documentation site from one definition. Part of Postman since January 2026.
  • StainlessThe generator behind many of the best-known AI SDKs. Its hosted product is winding down.
  • APIMaticThe longest-running commercial generator here, and the only one that converts between description formats.
  • liblabSDK generation shaped as a release pipeline. Part of Postman since November 2025.
  • KiotaMicrosoft's client generator, built so you do not need a separate SDK per API.
  • Hey APIThe TypeScript ecosystem's generator. One language, done properly.

All comparisons, the ground rules, and the wider field

Read the generated code#

The generator is MIT and open, and the catalog holds 600+ generated SDKs readable without installing anything.

Voxgig SDK GeneratorTalk to Voxgig

Get the Voxgig dispatch

Short notes on building SDKs, CLIs, REPLs, and MCPs for API-first teams, plus the occasional Fireside episode pick.

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