K-Culture GlossarySWords from the people who build
SDK
A ready-made toolkit for developers. When a company "releases an SDK," it's a signal that building on its technology just got easier.
In plain words
An SDK (Software Development Kit) is a build-it-yourself kit for developers. It bundles the parts, instructions, and examples you need to build something with a given technology — think of it as the software version of a model kit.
Here's how it relates to an API: if the API is the "order counter," the SDK is the "order helper set" the company pre-packages to make using that counter easier. You can walk up to the counter empty-handed, but with the kit you move faster and make fewer mistakes.
When you see an AI news headline like "Company X releases agent SDK," read it as: "building things with this company's technology just got easier, and they're trying to pull developers into their camp." Frequent SDK, API, and plugin announcements are a signal that a company isn't just selling a single product — it's chasing a platform, an ecosystem.
How it shows up in the news
"Released a free SDK for building agents" — this is a common move in the race to lock in developer ecosystems, and it's often followed by a rival's counter-announcement around the same time.
API vs SDK: what's the difference
The toolkit that makes that window easier to use, The window you call through
The two always show up together in announcements. A sentence like "we released an API and an SDK" never explains what each one actually is. The relationship is simple - the API comes first, and the SDK is something the company builds on top to make that API easier to use. You can use the API without the SDK, but not the other way around.
| Aspect | SDK | API |
|---|---|---|
| What it is | A bundle of parts, docs, and examples for that window | The ordering window itself |
| Can you skip it | You can skip it - it just takes more work | Without it, you can do nothing |
| Whose is it | Released separately per language - one for Python, one for JavaScript | Language-agnostic. You just follow the rules |
| What the announcement means | Building on it just got much easier - a signal aimed at bringing in developers | Others can now build on our technology |
| Analogy | A helper kit that places the order for you | An order window |
Rule of thumbIf the story is that a capability got opened up, it's the API. If the story is that using that capability got easier, it's the SDK.