Model Behavior Architect- Function Calling

Mistral AI

Job Overview

Location

London

Job Type

Full-time

Full Job Description

📋 Description

• Design and architect model behavior systems that enable precise, reliable, and safe function calling capabilities in Mistral AI’s frontier language models.
• Collaborate with research and engineering teams to define the semantic structure, constraints, and execution protocols for function calls integrated into Le Chat, La Plateforme, and Mistral Code.
• Develop evaluation frameworks to measure the accuracy, consistency, and safety of function calling behavior across diverse user prompts and enterprise use cases.
• Translate complex API specifications and domain-specific workflows into structured model instructions that ensure correct parameter binding, error handling, and state management.
• Work closely with product teams to align function calling behavior with user expectations in both consumer and enterprise applications, ensuring intuitive and predictable model responses.
• Identify edge cases and failure modes in function calling scenarios and implement mitigation strategies through prompt engineering, model fine-tuning, and behavioral gating.
• Document and standardize function calling patterns, schemas, and best practices for internal teams and external developers using Mistral’s open-source models.
• Participate in red teaming exercises to stress-test function calling systems against adversarial inputs, prompt injection attempts, and unintended model behaviors.
• Contribute to the iterative improvement of Mistral’s AI platform by providing feedback on model outputs, latency, and reliability in real-world function calling deployments.
• Maintain awareness of industry advancements in tool-use, agent architectures, and LLM orchestration to inform the evolution of Mistral’s function calling framework.
• Ensure all function calling systems comply with Mistral’s ethical AI principles, including transparency, accountability, and user control over automated actions.
• Support onboarding of enterprise clients by demonstrating and troubleshooting function calling integrations in their workflows.
• Work in close coordination with the safety and alignment team to prevent harmful, misleading, or unauthorized function executions by the model.
• Present findings and architectural decisions to cross-functional stakeholders, including product, legal, and compliance teams, to ensure alignment with business and regulatory requirements.
• Contribute to internal knowledge sharing through documentation, workshops, and peer reviews focused on model behavior design and function calling reliability.

🎯 Requirements

• Proven experience designing and implementing function calling or tool-use systems in large language models
• Deep understanding of API design, JSON schema, and structured output formats for AI models
• Experience working with open-source LLMs and their deployment in production environments
• Strong ability to analyze and debug model behavior failures in complex reasoning and tool-use scenarios
• Familiarity with prompt engineering techniques for controlling model actions and restricting unsafe outputs
• Experience collaborating with research and engineering teams to bridge theoretical models and practical applications

🏖️ Benefits

• Competitive salary and performance-based bonuses
• Comprehensive health and dental insurance
• Generous paid time off and flexible working hours
• Annual learning and development stipend for conferences, courses, or certifications
• Access to Mistral’s cutting-edge AI tools and platforms for personal and professional use
• Regular team retreats and in-person collaboration events in London, Paris, and other global offices

Skills & Technologies

Senior

Onsite

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Mistral AI

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About Mistral AI

Mistral AI is a Paris-based artificial intelligence company founded in 2023 that develops large language models and generative AI systems. The company creates open-source and commercial models optimized for performance, efficiency, and multilingual capabilities, serving enterprises and developers through APIs and cloud platforms. Its research focuses on advancing frontier AI while emphasizing safety, transparency, and European technological sovereignty.

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