AI Engineer - API & Integrations Team

Do you want to help us redefine how AI powers the future of Business Management software, not as an add-on, but as a core part of how people work, decide and grow? We're looking for engineers who treat AI as central to their craft, want to build and ship, and care about whether the thing they built actually worked.

Our Engineering team is a team of 200+ Product Engineers building a Business Management solution. Our core stack is Ruby on Rails and React but the interesting work right now is what we're building on top of that: agentic workflows, LLM-integrated features, systems that behave probabilistically rather than deterministically. The API & Integrations team sits at the intersection between product and platform, owning product surface while designing developer experiences for internal and external developers of integrations.

What You'll Do: Build product using Spec Driven Development (define clear specifications before shipping and use them to guide implementation, iteration and evaluation using the most powerful LLMs). Design and implement AI Skills — reusable, well-scoped AI capabilities that can automate and take actions safely within Factorial's workflows and when building integrations. Develop and maintain evaluation frameworks (Evals) to measure quality, correctness and reliability of AI outputs using automated and human-in-the-loop evaluations. Apply Retrieval-Augmented Generation (RAG) to ground AI responses in trusted, up-to-date company data. Design human-in-the-loop and agentic workflows that combine LLMs, rules, and user oversight to automate real business processes. Own systems end-to-end from problem definition and system design to shipping, monitoring and iteration in production.

What we're looking for: AI as a habit (you've built real AI-powered systems or workflows, not just experiments); proven impact; product-first thinking; speed & adaptability. Bonus points if you've worked with LLMs, skill-based agents, MCP, or other AI protocols. Strong candidates often have solid software engineering fundamentals (any language), experience shipping real products to production, and knowledge of APIs, cloud platforms, and system design.

We work on-site several days a week and support remote work when it makes sense. Headquartered in Barcelona with over 1,500 employees.