Senior Technical Writer, API Documentation

The Problem and the Role

OpenFX is on a mission to move money as freely as data, unrestricted by time zones, banking hours, or legacy systems. We are building the infrastructure that will power the next generation of cross-border payment systems for institutions. 

We are seeking a Senior Technical Writer to establish world-class API documentation and act as the translator between complex financial engineering and external developer adoption. We have built a world-class financial engine, but we need documentation that matches it.

This is a foundational role where you will own the documentation ecosystem from the ground up; architecting information systems, defining content standards, and directly influencing how global financial institutions integrate with our infrastructure. You'll set the bar higher than industry standards, building a knowledge system that turns complex FX liquidity and cross-border payment flows into a "Hello World" integration in under 15 minutes.

What You'll Actually Do & Own

• Architect the System: You will own the Information Architecture and the words. You will design the taxonomy that scales from a simple Quickstart guide to complex Treasury Operations references. You determine how we version, layer, and present information so it doesn't collapse under its own weight in two years.
• Own the Stack: You own the build- out of the API doc platform, while engineers build the APIs. You select the tech stack and implement tooling that enables engineers to contribute documentation efficiently while maintaining quality standards.
• Define the "Mental Models": You translate internal engineering logic into external developer understanding. You won't just document endpoints; you will explain concepts. You will write the definitive guides on handling idempotency, asynchronous webhooks, and multi-currency settlement states.
• Own the OpenAPI Workflow: You will implement and enforce a "Design First" or strictly governed "Code First" workflow where OpenAPI/Swagger specs are treated as a product contract. You ensure automated reference generation from these workflows are accurate, typed, and complete.
• Drive API Design Feedback: You will sit in Product, Engineering and Design reviews. You are the "First User." If an API is too hard to explain in writing, it is too hard to use. You will have the authority to push back on engineering to improve parameter naming and consistency before code hits production. You will create feedback loops between customer integration challenges and documentation improvements.

What Success Looks Like

• Launch V1 Developer Portal: A public API doc portal (References + Guides + Changelog) is live, searchable, and accurate.
• Expand Coverage: 100% of public endpoints have accurate request/response examples in at least three languages
• Deflection Rate: You reduce "Instructional" support tickets (questions asking "how do I do X?") by 40%.
• Integration Velocity: Partner with Product and Engineering to drive the "Time to First API Call" down to <15 minutes. You own the Quickstart guides, code snippets, and onboarding tutorials that make this speed possible, while advocating for the product changes needed to remove friction.

Requirements

• 5+ Years in API Documentation: You have specifically documented REST APIs for B2B or infrastructure products. You can point to public docs you architected in the past.
• Docs-as-Code Native: You treat documentation as software. You are fluent in Markdown, Git, and CI/CD workflows. You don't copy-paste into a CMS; you commit to a repo.
• Engineering Fluency: You can read code well enough to extract logic independently. You understand distributed system concepts (Latency, Rate Limiting, Eventual Consistency).
• The "Teacher" Mindset: You can demonstrate a time you took a complex non-linear concept and simplified it into a linear guide.
• The "Why" over the "What": Your portfolio demonstrates that you write about why a developer uses an endpoint, not just what the endpoint does.
• High ownership and autonomy: You are comfortable building documentation systems from scratch, establishing processes, and making architectural decisions.
• Financial services or Fintech Context: You know the difference between "Authorized" and "Settled." You have documented payments, trading, or banking APIs before.

Preferred

• Interactive Docs: Experience implementing interactive code playgrounds or "Try it now" buttons within documentation.
• Multimedia documentation skills: Creating video tutorials, interactive demos, architecture diagrams, sequence diagrams, or other visual learning materials that complement written documentation.
• Understanding of AI-assisted development workflows and how to optimize documentation for LLM consumption alongside human readers.

Why This Role?

• Founding Member: You are the first hire in this function. As we scale, you will define the hiring standards, the voice, and the culture of the documentation team.
• Greenfield Architecture: You aren't inheriting legacy debt. You get to build the system right the first time selecting the stack, the taxonomy, and the governance model.
• The Frontier of Finance: You will learn the inner workings of global finance (FX liquidity, settlement, treasury), but you will apply them to the new payment stack as well as legacy rails of the past.
• Shape the Industry Narrative: Our technology is novel. You aren't just describing features; you are teaching developers how to think about the future of money and defining the vocabulary of the industry.
• The Team: You are joining a team of ex-Stripe, J.P. Morgan, and Kraken engineers. We are backed by Accel and Lightspeed, and we value documentation as a core part of the product.

Developer-focused fintech enabling cross-border payments.