> For the complete documentation index, see [llms.txt](https://docs.lingoql.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lingoql.com/sub0/apis-abi.md).

# APIs (ABI)

Sub0 APIs are defined with a declarative ABI.

You describe the endpoint, the actions it runs, and the rules around it.

That means less backend glue and a faster path to production.

### Start with the basics

Read these pages in order:

1. [Structure](/sub0/apis-abi/structure.md)
2. [Accessors](/sub0/apis-abi/accessors.md)
3. [Payload Validation](/sub0/apis-abi/payload-validation.md)
4. [Authentication](/sub0/apis-abi/authentication.md)
5. [Making API Requests](/sub0/apis-abi/making-api-requests.md)

### Then move into real workflows

* [Example APIs (ABI)](/sub0/apis-abi/example-apis-abi.md)
* [Action Chaining](/sub0/apis-abi/action-chaining.md)
* [File Uploads](/sub0/apis-abi/file-uploads.md)
* [Caching](/sub0/apis-abi/caching.md)
* [Queueing](/sub0/apis-abi/queueing.md)
* [Cron Jobs](/sub0/apis-abi/cron-jobs.md)
* [Webhooks](/sub0/apis-abi/webhooks.md)
* [Websockets](/sub0/apis-abi/websockets.md)

### Finish with copy-first patterns

Use [Practical Examples](/sub0/apis-abi/practical-examples.md) when you want full, production-style flows you can adapt fast.

### Why this matters

The ABI is the shortest path from idea to working backend.

Learn the basics once.

Then reuse the same model for auth, data access, uploads, jobs, and real-time APIs.


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