Agent Architect - Pencil

About Pencil

At Pencil, we are driving innovation in advertising technology through our state-of-the-art SaaS product, which harnesses Generative AI to redefine content creation. Our mission is to make AI the default in advertising without replacing creative people. To achieve this, we make sure our technology is accessible to global brands, small businesses, and creative individuals alike.

We’re building the agentic OS for marketing. Rather than simply integrating generative AI, we are building the machine that makes it professional, brand-safe, and scalable—moving beyond text-in/text-out interfaces toward complex multi-agent architectures that handle nuanced creative demands.

We are looking for an Agent Architect who thinks in systems. You will be responsible for the "brain" of Pencil: designing 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 agents are robust, predictable, and capable of high-fidelity output across text, image, and video.

This is a client-facing technical role where you'll collaborate with brand and agency stakeholders, lead discovery conversations, decompose business problems into agent architectures, and explain design choices in plain language.

Your work centers on two key pillars:

1. Core Systems: Designing and scaling foundational agents that power the Pencil SaaS platform.
2. Client Solutions: Architecting custom workflows for world-class brands that require specific brand DNA and complex creative logic.

Key Responsibilities

• Agent Architecture: Design and implement multi-agent workflows, including task decomposition, state management, and tool-use (RAG, API integrations, etc.).
• Systematic Optimization: Implement rigorous evaluation frameworks (e.g., LLM-as-a-judge, promptfoo, 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. Lead structured discovery sessions, decompose ambiguous business problems into buildable agent workflows, and present trade-offs (cost, latency, reliability) to non-technical stakeholders.

Your Background

• 3+ Years of Direct GenAI Experience: Deep technical and intuitive understanding of LLMs (GPT-4, Claude, Gemini) and multimodal models (Stable Diffusion, Midjourney, Video Gen).
• Systems Thinking: Focus on latent space, context windows, and multi-agent input/output dynamics rather than standalone prompts.
• Technical Literacy: Comfortable working with Python, JSON structures, and API documentation. Strong grasp of agent orchestration patterns (task decomposition, tool use, state management).
• Evaluation Obsession: Proven experience benchmarking and A/B testing AI outputs with systematic evaluation frameworks.
• Creative/Technical Bridge: Ability to translate subjective creative feedback into concrete system adjustments and represent the technology directly to clients.
• Client-Facing Problem Decomposition: Demonstrated experience in solutions architecture, forward-deployed engineering, or technical consulting leading discovery and scoping.
• Plain-Language Communication: Ability to clearly explain failure modes, eval results, and architectural trade-offs to non-technical executive stakeholders.

Benefits

• 25 days PTO plus public holidays (Flexible Time Off scheme)
• Health insurance / private medical cover
• Monthly stipend for wellness, fitness, and learning & development
• Remote work (work from anywhere in your home country)
• Enhanced parental leave policies (birth, adoption, surrogacy)
• Flexible working hours
• Access to the Pencil office in The Shard, London (when visiting the UK)