ModelRefs / OpenAI API — AI Glossary

OpenAI API — AI Glossary

OpenAI's cloud API providing access to GPT-4o, o3, embeddings, DALL-E, Whisper, and other models via REST endpoints.

Overview

The OpenAI API is the most widely integrated LLM API. Key endpoints: /v1/chat/completions (text generation), /v1/embeddings, /v1/images/generations, /v1/audio/transcriptions. The OpenAI-compatible interface has become the de facto standard adopted by dozens of other providers. Billing per token (input and output priced separately).

Reference details

Topic	infrastructure
Last reviewed	2026-06-24

Example: “OpenAI-compatible” describes the request, not the behaviour

Dozens of providers accept the same request shape — a messages array, a model string, temperature, tools — which is why swapping a base URL appears to work. What varies underneath: which sampling parameters are honoured versus silently ignored, whether tool calling is supported and in which dialect, whether structured output guarantees schema conformance or merely requests it, how streaming chunks are framed, and what the error codes mean. The shape is portable; the behaviour is not. Treat a provider swap as a change requiring the same evaluation run as a model swap, because it is one.

Commonly confused with

The chat completions shape is the compatibility standard; it is not the only interface OpenAI offers, and newer stateful endpoints deliberately differ by keeping conversation state server-side. Compatibility claims also cover only the endpoint surface — rate limits, retention policies, data-training terms and regional routing are per-provider and are usually the reasons the choice matters.

When to use it

Reach for it when:

As the default integration target, since it maximises provider portability
Gateways and routers, which normalise other providers into this shape
Prototyping against a hosted model before deciding on self-hosting

Reach for something else when:

Assuming a compatible endpoint behaves identically — verify parameters and tool support
Where you need provider-specific features that the shared shape cannot express
Hard-coding a floating model alias in production; pin the version

Continue your research

Use these connected ModelRefs sections to compare alternatives, inspect implementation paths, and review the evidence and governance boundaries relevant to OpenAI API — AI Glossary.

Frequently asked questions

What is OpenAI API?