Responses API

The Responses API is OpenAI's unified, agent-centric interface: it streamlines multi-turn interactions and natively integrates powerful tools like web and file search.

This is OpenAI's flagship API for building advanced AI agents, replacing the complexity of the Chat Completions and Assistants APIs with a single, streamlined endpoint. It enables stateful, multi-turn conversations and natively supports multimodal inputs (text, images) and outputs. Developers gain immediate access to built-in tools (web search, file search, code interpreter) and can utilize reasoning models like GPT-5 for a 5% performance boost on tool-calling evaluations, simplifying complex agentic workflows with less code.

https://platform.openai.com/docs/api-reference/responses