Mistral launches its Responses API in public preview: OpenAI Responses-compatible, returning the answer, reasoning and tool calls as separate items for building agents
Mistral AI announced on X on Oct 28 that its Responses API is in public preview, positioned as the interface for building agents on Mistral. The official docs say it uses the OpenAI Responses format, and each response's output array carries the models messages, its reasoning and its function calls as separate items, which is easier to handle step by step than Chat Completions. The preview is stateless, so the app keeps the conversation history and sends it back; it supports text, image and file input, JSON Schema structured output, streaming events, client-executed function calls, reasoning.effort, and token counting via POST /v1/responses/input_tokens. It is served in the EU and US on Mistral AI Cloud Inference. The same thread says Mistral now also serves DeepSeek V4.1 Flash (public preview) and GLM 5.3 Flash (generally available).
Key Takeaways
- The Responses API is in public preview and uses the OpenAI Responses format, so existing Responses integrations can move to Mistral more easily
- Each response splits the answer, reasoning and function calls into separate output items, which suits step-by-step agent loops
- The preview is stateless: the app keeps the history and sends earlier output items back along with function_call_output results
- It supports image and file input, JSON Schema structured output, streaming, function calling (including namespaces), reasoning.effort and token counting via /v1/responses/input_tokens
- It is served in the EU and US on Mistral AI Cloud Inference; Mistral also added DeepSeek V4.1 Flash (preview) and GLM 5.3 Flash (GA)