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

# OpenAI and OpenAI-compatible

> How OpenAI-style providers run through Compose.

OpenAI-style providers share a familiar wire shape: chat completions, Responses-style requests, embeddings, images, audio, and tool calls.

Compose uses that family for OpenAI itself and for providers whose API follows the OpenAI wire closely enough to use the shared lowering path.

## Public IDs and upstream IDs

Provider aliases keep public model IDs unambiguous:

```text theme={null}
openai/gpt-5.5 -> provider openai, upstream gpt-5.5
gpt-5.5        -> provider azure, upstream gpt-5.5
```

The public ID is used for catalog responses, receipts, and metering subjects. The upstream ID is what the adapter sends to the provider.

## Tools and reasoning

Some OpenAI-family models require the Responses wire when function tools and reasoning parameters are combined. The adapter handles that switch and still returns an OpenAI-compatible response shape to external clients.

## Related

* [Tools](/inference/tools)
* [External clients](/inference/external-use/overview)