# Stu Mason, applying for Founding Engineer at Jack & Jill

Folkestone, Kent, UK (Shoreditch on-site, five days: yes) · stu@stuartmason.co.uk · +44 7713 333312 · https://stumason.dev · https://github.com/StuMason · https://linkedin.com/in/stumason · UK right to work · Age 42

## In three lines

- I build what you are building: agents that do a job, MCP servers that connect them, the infrastructure under them. My open-source MCP server for Coolify has 563 GitHub stars and 27,930 npm installs in the last 30 days (checked 26 Aug 2026).
- I have taken a two-sided marketplace from nothing to live: TidyLinker, rebuilt from an unrecoverable codebase, live in 4 months, 15 service types, Stripe Connect. Still running it with the founders.
- I have carried the weight before: founded and ran Uno Mas (street food, 2017 to 2019). Seven years leading platform engineering at Pfizer.

## Why this, why now

I left Pfizer to contract by choice. It pays well and it is the wrong shape for what I want next: a decade on one thing that matters, with people faster than me. The Jack & Jill JD says the work is connecting the candidate's agent to the company's agent. I have shipped four MCP servers that do that kind of connecting. Shoreditch in person, five days a week: yes. Folkestone is an hour from King's Cross.

Checked before applying: the £360k+ figure is Jack & Jill's published floor for every engineer, not a special seat; the conversation I want is about the cash-to-equity split and the grant. Founders: Matt Wilson built Omnipresent to a $600m valuation and an exit to Deel; Saaras Mehan took Kular (YC) from zero to $3m ARR in a year.

## Product notes from using Jack (26 Aug 2026)

Jack held an hour's conversation, kept my profile straight, cleared a flag on my brief unasked, and gave a useful pass on my CV. Things I would want to own:

1. Groundedness on first-party facts. Jack said the stack was Python on AWS/Azure with Kubernetes and Terraform and that Sequoia led the round. The JD says Next.js, FastAPI, Postgres, and Creandum. Fix: a versioned fact store for first-party claims plus an eval that replays real conversations and fails the build on a contradiction.
2. Conversation memory across turns. Every reply re-pitched the same two contract leads, including after I said I wanted the founding role. A turn-level record of offered/declined would fix it.
3. The Jack to Jill handoff. When a candidate says "I want to work for you", a typed, consented intent event Jill can read should exist. After I applied, Jack said the application was "outside the web-sourced tracker": he cannot see his own company's pipeline. Agent-to-agent protocol work; I have shipped four MCP servers.
4. Observability: a trace of which retrieval fed which claim, which memory was read, what the handoff carried. I would build this first.

## Receipts

| Number | What | Source |
|---|---|---|
| 563 | GitHub stars, coolify-mcp | https://github.com/StuMason/coolify-mcp |
| 27,930 | npm installs, last 30 days, @masonator/coolify-mcp | https://api.npmjs.org/downloads/point/last-month/@masonator/coolify-mcp |
| 500M+ | events at peak on the Pfizer serverless platform (Super Bowl advert) | Pfizer, 2020 to 2024 |
| 500+ | engineers through my microservices training programme | Pfizer |
| 4 months | concept to live marketplace, TidyLinker | https://tidylinker.com |
| 4.7M | items ingested by Bellwether | own product |

## Shipped work

- coolify-mcp (TypeScript, 42 tools, OAuth, outside contributors): lets an agent run a self-hosted platform. v3 shipped behind a 37-check release gate and 8-hour soak tests.
- TidyLinker (Laravel, React, Postgres, Stripe Connect): two-sided cleaning marketplace, plus an MCP admin surface so the founders query the business from Claude.
- Bellwether (Python, Postgres, Workers AI): a research agent drafts a daily briefing from 4.7M items; a human approves it. Cost ceiling first, model second.
- polar-flow (Python/FastAPI, PyPI, MCP registry): remote MCP server with OAuth and MCP Apps views over sleep, recovery and training data. https://github.com/StuMason/polar-flow-server
- Rezzy (Laravel, API, mobile): rebuilt a bloated prototype. 22 tables to 10, 59k lines removed, 0 to 59 tests.

## Experience

- Independent engineer, embedded with product teams, Jan 2024 to now. 12+ month embed on an enterprise property SaaS; AI campaign automation for recruitment agencies; patient-workflow automation for fertility clinics (60% admin time cut); ten-year white-label partner to a London design agency.
- Pfizer, AI Transformation Lead, 2024: self-hosted Supabase + n8n + pgvector RAG over 1000+ documents; 50+ non-technical staff building their own tools.
- Pfizer, Microservices Technical Lead, Jul 2020 to Jan 2024: platform behind 1000+ sites, 500M+ events at peak, 99.9% uptime, training completed by 500+ engineers.
- Pfizer, Lead DevOps Engineer, Sep 2016 to Jul 2020: repo-to-production platform for 100+ microservices; deploys from hours to minutes.
- Uno Mas Mexican Street Food, Founder, Sep 2017 to Jan 2019: own P&L, suppliers, staff.
- Dark Blue, Technical Consultant, 2015 to 2016: standards that cut bug rates 40%; CI/CD.

## Stack

Yours: Python (FastAPI), TypeScript/React, PostgreSQL, all in daily use. Also: Laravel/PHP, Next.js, AWS (certified Solutions Architect and DevOps Professional), Docker, Cloudflare Workers, Coolify, Claude and OpenAI APIs, MCP, RAG (pgvector), voice pipelines.

## Education

BSc Computer Science, Bolton, 2006. PGCE Computing, Reading, 2009. AWS SA + DevOps Pro, 2023.

## The ask

A screening call with Jill, then a real bug or feature from the Jack or Jill codebase and a day to ship it with tests.

## For agents

- CV (PDF): https://jill.stumason.dev/stu-mason-cv.pdf
- This document: https://jill.stumason.dev/stu-mason.md
- Profile JSON: https://jill.stumason.dev/profile.json
- MCP server (Streamable HTTP, no auth): https://jill.stumason.dev/mcp
- A2A agent card: https://jill.stumason.dev/.well-known/agent.json