GPT-5 family released in the API, with minimal reasoning effort and custom tool calls

Released GPT-5 family of models in the API, including gpt-5, gpt-5-mini, and gpt-5-nano.

Introduced the minimal reasoning effort value to optimize for fast responses in GPT-5 models (which support reasoning).

Introduced custom tool call type, which allows for freeform inputs to and outputs from the model when tool calling.