Agent Architect

At Pencil, we’re building the agentic OS for marketing. We aren't just using integrating generative AI; we are building the machine that makes it professional, brand-safe, and scalable. We’re moving beyond simple text-in/text-out interfaces toward complex multi-agent architectures that can handle the nuanced demands of global brands and the agility of small businesses. We are looking for an Agent Architect who thinks in systems, not just sentences. You will be responsible for the "brain" of Pencil—designing the agent logic, tool-calling structures, and evaluation loops that power our core creative engine and bespoke client solutions. The Role: Architecting the Creative Brain You won’t just be "prompting"; you will be engineering behavior . You will bridge the gap between creative intent and machine execution, ensuring that our agents are robust, predictable, and capable of high-fidelity output across text, image, and video. Your work will fall into two high-impact pillars: Core Systems: Designing and scaling the foundational agents that power the Pencil SaaS platform. Client Solutions: Architecting custom workflows for world-class brands that require specific "brand DNA" and complex creative logic. Job Responsibilities Agent Architecture: Design and implement multi-agent workflows, including task decomposition, state management, and tool-use (RAG, API integration, etc.). Systematic Optimization: Move beyond "vibe-based" testing. Implement rigorous evaluation frameworks (e.g., using LLM-as-a-judge, promptfoo, or DSPy) to measure and improve agent performance at scale. Scalable Frameworks: Develop reusable agents and prompt libraries that allow the platform to serve 1,000+ brands with unique voices simultaneously. Cross-Functional Engineering: Partner with AI Engineering and Product teams to determine which behaviors should be handled via prompting, RAG, or fine-tuning. Client Architecture: Act as the technical lead for complex client deployments, translating high-level creative briefs into deterministic AI workflows. What We’re Looking For 3+ Years of Direct GenAI Experience: You have a deep, intuitive, and technical understanding of LLMs (GPT-4, Claude, Gemini) and multimodal models (Stable Diffusion, Midjourney, Video Gen). Systems Thinking: You don’t just write a prompt; you think about the latent space, the context window, and how one agent's output becomes another’s input. Technical Literacy: While this isn't a "Software Engineer" role, you should be comfortable with Python, JSON structures, and API documentation. Experience with orchestration frameworks (LangChain, CrewAI, AutoGen) is a major plus. Evaluation Obsession: You believe that if you can’t measure a prompt’s performance, you shouldn’t ship it. You are familiar with benchmarking and A/B testing AI outputs. The "Creative/Technical" Bridge: You can sit in a room with a Creative Director and translate "make it feel more punchy" into a temperature adjustment and a few-shot prompting strategy. You’ll Thrive Here If... You find "hallucinations" to be a logic puzzle to be solved, not just a bug. You are excited by the challenge of making an AI follow a 50-page brand book with 100% fidelity. You want to build the infrastructure that defines how the next generation of advertising is created. KPI & Success Measures System Reliability: Reducing the "failure rate" of complex agent workflows. Architectural Efficiency: Minimizing token usage/latency while increasing output quality. Brand Alignment: Scoring of agent outputs against specific brand guidelines using automated evaluation tools. Scale: Successful rollout of core agents used by the entire Pencil user base. Benefits 25 days PTO plus public holidays, although we operate a Flexible Time Off scheme Health insurance / private medical cover Monthly stipend towards wellness, fitness, and learning and development Remote - work from anywhere in your home country Enhanced parental leave policies, whether you become a parent through birth, adoption or surrogacy Access to our Pencil office in The Shard, London for our UK employees Flexible working hours