Mistral AI introduces the Responses API in public preview for building agents

Mistral AI launched the Responses API in public preview on 28 October 2026, introducing a dedicated endpoint designed for multi-step AI agents and tool-using applications. Until now, developers building agents on Mistral models had to manage conversation history, tool execution loops, and intermediate chain-of-thought traces inside the older Chat Completions format, often parsing reasoning text and function arguments out of combined message blocks.

The Responses API restructures every turn into discrete, typed output items: the model’s intermediate reasoning steps, structured tool or function calls, and the final user-facing answer are returned as separate array elements in the response object. That separation lets application code log or hide internal reasoning traces, validate tool inputs before execution, and resume multi-turn agent state without re-serialising the entire prompt history on every step.

The endpoint is available immediately in public preview across Mistral AI’s developer platform and works with all chat models hosted by Mistral, including Large 4.