GPT-5 is OpenAI's flagship LLM — strong reasoning, tool use, vision, and JSON mode. Drop-in for anything you'd use GPT-4o for.
curl https://oneapikey.app/v1/v1/chat/completions \
-H "Authorization: Bearer $ONEAPIKEY_API_KEY" \
-H "X-APIMarket-Product: gpt-5" \
-H "Content-Type: application/json" \
--data '{"model":"openai/gpt-5","messages":[{"role":"user","content":"hi"}]}'