# Speakeasy and Voxgig, compared

> Commercial SDK generation with the widest non-SDK output in this comparison. A closed-source generator behind a CLI you run in your own CI, sold per language. Generates Terraform providers and MCP servers as well as SDKs, and expresses customization as OpenAPI Overlays rather than a private config format. Published by Voxgig, which makes one of the two tools. Facts checked 7 September 2026.

## What it 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.

## Facts

- Made by: Speakeasy
- Licence: Proprietary. Generated SDKs are yours
- Cost: Free tier, then per language per month
- Site: speakeasy.com (https://www.speakeasy.com)
- Notable output: Terraform providers, MCP servers

## What Speakeasy does that Voxgig does not

### 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

| | Speakeasy | Voxgig |
| --- | --- | --- |
| Licence | Generator closed source. Generated SDKs are yours | Generator MIT. Generated SDKs are yours |
| Cost | Free tier for one SDK with an endpoint cap, then per language per month | Free |
| Account needed | Yes | No |
| Language targets | About 10, including Unity | 22 bundled language targets, more from packages |
| Terraform provider | Yes | No |
| MCP server | Yes | Yes |
| CLI and REPL over your API | No | Yes |
| Customization | OpenAPI Overlays, `gen.yaml`, custom code regions | Model, templates, components, features, targets, packages, all in your repo |
| Support | Commercial, with an SLA on paid plans | Community, or a paid API Experience engagement |

## 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. A correction changes the page and moves its checked date.

## First-party sources

- [speakeasy.com](https://www.speakeasy.com)
- [Speakeasy pricing](https://www.speakeasy.com/pricing)
- [Speakeasy's own comparison of this field](https://www.speakeasy.com/blog/comparison-sdk-generators-openapi)
- [The OpenAPI Overlay specification](https://spec.openapis.org/overlay/latest.html)

## The other comparisons

- [All SDK generator comparisons](https://voxgig.com/sdk/comparisons): the index, the method, and the wider field.
- [OpenAPI Generator](https://voxgig.com/sdk/comparisons/openapi-generator): The community generator most APIs have shipped an SDK from at least once.
- [Fern](https://voxgig.com/sdk/comparisons/fern): SDKs and a documentation site from one definition. Part of Postman since January 2026.
- [Stainless](https://voxgig.com/sdk/comparisons/stainless): The generator behind many of the best-known AI SDKs. Its hosted product is winding down.
- [APIMatic](https://voxgig.com/sdk/comparisons/apimatic): The longest-running commercial generator here, and the only one that converts between description formats.
- [liblab](https://voxgig.com/sdk/comparisons/liblab): SDK generation shaped as a release pipeline. Part of Postman since November 2025.
- [Kiota](https://voxgig.com/sdk/comparisons/kiota): Microsoft's client generator, built so you do not need a separate SDK per API.
- [Hey API](https://voxgig.com/sdk/comparisons/hey-api): The TypeScript ecosystem's generator. One language, done properly.
- [Voxgig SDK Generator](https://voxgig.com/sdk)