Software Engineer (AI)

Numeral is building the automation backbone for internet commerce — starting with the painful world of sales tax compliance. We handle everything from registration to remittance, delivering a white-glove service so e-commerce businesses can stay laser-focused on what they do best: growing their products, customers, and teams.

We’re one of the fastest-growing companies from Y Combinator’s W23 batch, backed by top-tier investors including Benchmark Capital. Our team has deep roots from the early days at Stripe, Airbnb, Notion, and other breakout companies — and now we’re bringing that same level of craft, speed, and ambition to a space that’s long overdue for reinvention.

Numeral is small but mighty. Growth is already borderline unmanageable — which means every hire we make now will directly shape the trajectory of the company. If you’re excited about joining as an early team member and want the kind of ownership that defines careers, we want to meet you.

Running an online business today means wearing a thousand hats — most of them not the reason founders started their company. Our mission is to eliminate the administrative and accounting burdens that distract businesses from doing what they love.

We’ve already helped hundreds of merchants avoid the headache of building giant finance teams just to manage tax compliance. Tomorrow, we’re scaling that impact even further: building the automation layer that lets internet businesses stay nimble, compliant, and future-proof.

Numeral has raised over $57M, now serves over 2,500 paying customers and we have more than tripled our revenue every year in our history.

We’re looking for a Foundational AI Engineer who thrives in ambiguity, enjoys building real-world AI systems end-to-end, and wants to define the technical and architectural foundations of an early-stage startup.

This is a hands-on role for someone who wants to design and implement LLM-powered automation systems: model orchestration, tool calling, MCP-style integrations, agentic workflows, and automation-driven tooling, while being familiar with a traditional full-stack development environment. You should also extensively use AI-powered tools for development.

You’ll work closely with product and leadership to concretize AI ideas into production-grade systems that customers rely on daily.

• Design, build, and operate production AI systems, including tool-calling agents, model orchestration layers, and RAG.

• Implement and maintain AI integrations using modern frameworks, MCP servers, and external model providers.

• Build and evolve scalable backend services and APIs that power automated workflows and customer-facing features.

• Think in automation and workflows: design systems using tools like n8n, Claude Code-style agents, or similar orchestration approaches where appropriate.

• Make architectural decisions that balance latency, cost, reliability, and iteration speed.

• Own infrastructure, observability, and performance for both AI and non-AI services.

• Collaborate closely with product, design, and data teams to ship features that solve real customer problems.

• Help define engineering best practices, AI safety/reliability norms, and our overall technical culture.

• 7+ years of experience building products in high-growth environments.

• 2+ years of experience building with LLMs.

• Avid use of state-of-the-art AI development tools such as Cursor and Claude Code.

• Fluency with backend technologies like PostgreSQL, Redis, and cloud services (AWS preferred).

• Experience with frontend development, especially TypeScript and its ecosystem.

• Strong product sense, balancing performance, flexibility, and speed.

• Comfortable working in dynamic startup environments with evolving needs.

• Excellent communication and collaboration skills.

• Experience in payments, tax, accounting, or regulatory tech.

• Experience with automation tools (n8n, Zapier-style systems, workflow engines) or building internal automation platforms.

• Familiarity with MCPs, tool calls, agent frameworks, or model orchestration patterns.

• Understanding of vector databases and concepts (such as Pinecone, HNSW).

• Competitive salary and equity - you'll share directly in the company's success

• Full medical, dental, and vision coverage

• Wellness perks like Headspace and the Peloton One App

• 401(k) to help you build long-term financial security

• Lunch and snacks when you're in the office

• Regular team offsites and company events as we grow

• A culture built on ownership - your work matters and people will see it!