Overview
API access to OpenAI’s GPT and Codex models for building custom coding agents, with reasoning models, tool use, and Realtime support.
Details
The OpenAI API provides programmatic access to OpenAI’s models including GPT-4, GPT-5, o-series reasoning models, and codex-1 (specialized for coding agents). The API supports tool use, Responses API for complex agent loops, file processing, and Realtime audio for voice agents. Many coding products use OpenAI as one of multiple model providers. OpenAI is foundational infrastructure for much of the AI coding agent ecosystem.