> ## Documentation Index
> Fetch the complete documentation index at: https://kiosapi.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# KiosAPI — OpenAI-Compatible Multi-Model AI Gateway

> KiosAPI is a unified gateway giving you OpenAI-compatible access to GPT, Claude, Gemini, and more through a single endpoint and a single API key.

KiosAPI is a unified API gateway that gives you OpenAI-compatible access to a wide range of large language models — including GPT, Claude (Anthropic), and Gemini (Google) — through a single endpoint. Instead of juggling multiple accounts, keys, and SDKs, you point your existing tools at KiosAPI and let it handle the routing.

## Model Compatibility

KiosAPI exposes an **OpenAI-compatible API**, so you can use the official `openai` Python or Node.js SDK, `langchain`, `litellm`, or any other library built for the OpenAI API without changing your application logic. Set the `base_url` to the KiosAPI endpoint, supply your KiosAPI key, and your code works out of the box.

KiosAPI also supports native Claude and Gemini endpoint formats, so you can integrate using whichever SDK or convention your project already uses.

| Format                | Endpoint Path                            | Compatible SDK                      |
| --------------------- | ---------------------------------------- | ----------------------------------- |
| **OpenAI format**     | `/v1/chat/completions`                   | OpenAI SDK (`openai`)               |
| **OpenAI new format** | `/v1/responses`                          | OpenAI SDK (`openai` ≥ 1.50)        |
| **Claude native**     | `/v1/messages`                           | Anthropic SDK (`@anthropic-ai/sdk`) |
| **Gemini native**     | `/v1beta/models/{model}:generateContent` | Google GenAI SDK (`@google/genai`)  |

## Authentication Methods

Each endpoint format expects your API key to be passed differently in the HTTP headers. Use the table below to match the correct auth header to the endpoint you're calling.

| Format            | Header                                                | Example                                      |
| ----------------- | ----------------------------------------------------- | -------------------------------------------- |
| **OpenAI**        | `Authorization: Bearer sk-xxx`                        | `Authorization: Bearer sk-kilo-xxxxxxxxxxxx` |
| **Claude native** | `x-api-key: sk-xxx` + `anthropic-version: 2023-06-01` | `x-api-key: sk-kilo-xxxxxxxxxxxx`            |
| **Gemini native** | `x-goog-api-key: sk-xxx`                              | `x-goog-api-key: sk-kilo-xxxxxxxxxxxx`       |

<Warning>
  Use the correct auth header for the endpoint you're calling. For example, the Claude native endpoint (`/v1/messages`) expects `x-api-key`, **not** `Authorization: Bearer`. Sending the wrong header returns a `401 Unauthorized` error.
</Warning>

## Official Documentation References

For deeper understanding of each API format, refer to the official provider documentation:

* [OpenAI API Reference](https://platform.openai.com/docs/api-reference)
* [Claude (Anthropic) API Reference](https://docs.anthropic.com/en/api)
* [Gemini (Google) API Reference](https://ai.google.dev/api)

<CardGroup cols={2}>
  <Card title="Authentication" icon="key" href="/authentication">
    Learn how to pass your KiosAPI key for each endpoint format.
  </Card>

  <Card title="API Base URL" icon="link" href="/api-base-url">
    Find the correct base URL and configure it in your SDK.
  </Card>
</CardGroup>