Today, we’re adding new built-in tools to the Responses API—our core API primitive for building agentic applications. This includes support for all remote Model Context Protocol (MCP) servers⁠(opens in a new window), as well as tools like image generation⁠(opens in a new window), Code Interpreter⁠(opens in a new window), and improvements to file search⁠(opens in a new window). These tools are available across our GPT‑4o series, GPT‑4.1 series, and OpenAI o-series reasoning models. o3 and o4-mini can now call tools and functions directly within their chain-of-thought in the Responses API, producing answers that are more contextually rich and relevant. Using o3 and o4-mini with the Responses API preserves reasoning tokens across requests and tool calls, improving model intelligence and reducing the cost and latency for developers.