Model Behavior Architect- Function Calling

About Mistral

At Mistral AI, we believe in the power of AI to simplify tasks, save time, and enhance learning and creativity. Our technology integrates seamlessly into daily work. We democratize AI through high‑performance, optimized, open‑source models and solutions. Our platform meets enterprise and personal needs, featuring Le Chat, La Plateforme, Mistral Code, and Mistral Compute. Our team operates across France, USA, UK, Germany, and Singapore, driven by a collaborative, low‑ego culture.

About the Role

As a Model Behavior Architect on the Function Calling team, you define and measure how large language models use tools, invoke functions, and orchestrate complex agentic workflows.

What You Will Do

• Interact with models to identify where function‑calling and tool use behaviour can be improved
• Gather internal and external feedback on tool‑calling behaviour to scope areas for improvement
• Design and implement evals, data guidelines, data generation, and synthetic tool environments and APIs
• Identify and fix edge‑case behaviours, such as malformed arguments, hallucinated functions, and incorrect tool selection, through rigorous testing
• Develop robust evaluation pipelines for the function‑calling capabilities of model candidates
• Work collaboratively with AI scientists

About You

• Deep understanding of API design, structured outputs, and schema specification (e.g., JSON Schema); or engineering and code behavior; or LLM agents with reasoning, planning, and multi‑step tool use
• Experience in training and optimising model behaviour
• Expertise building robust evaluations
• Thrives in dynamic and technically complex environments
• Track record of delivering innovative, out‑of‑the‑box solutions to address real‑world constraints

What We Offer

• Competitive salary and equity
• Health insurance
• Transportation allowance
• Sport allowance
• Meal vouchers
• Generous parental leave policy
• Visa sponsorship