API Doc Portfolio

I have written API documentation since 2014. My LinkedIn profile: https://www.linkedin.com/in/peterdavidgustafson.

Over the past 12 years I have consulted for some of the most recognized names in tech and finance — Coinbase, Epic Games, WEX Bank, and Discover Card. I have also worked with Interactive Brokers, Alchemy, ShipEngine, Stripe, and others. In 2022 I moved into AI consulting. I now integrate Claude, Gemini, and Copilot directly into documentation workflows. This cuts doc cycle times in half. It also reduces developer support tickets by up to 65%.

I specialize in REST and SOAP API docs, OpenAPI/Swagger specs, OAuth 2.0, and docs-as-code in Markdown. I build on platforms like Mintlify, Docusaurus, and ReadMe. Every project below is real work. Published pages and raw Markdown files are included.

— Peter Gustafson

Consulted with Discover’s product owners and API engineers to modernize their partner-facing payments developer portal. Restructured docs covering token provisioning, cryptogram generation, and second-factor authentication. Delivered standardized request/response templates and parameter definition tables now used across their portal.Designed reusable doc templates that reduced time-to-publish for new endpoint docs across the partner portal team. Some of work is  below:

PyTorch / TensorFlow / ONNX ML workflow documentation (in progress). Self-directed project building hands-on skills in Python-based ML frameworks. Currently creating sample documentation for model training, export to ONNX format, and inference pipelines to support future API/SDK guides for AI developers.

Consulted on elevating IB’s TWS API documentation to best-in-class standards. Coached junior technical writers on formalizing API documentation into scalable templates used in developer onboarding flows. Delivered Connectivity, Streaming Market Data, and Troubleshooting docs.Below are examples of my work at IB.

Hired to update internal documentation and Salesforce architecture diagrams for new engineering cohorts at one of DeFi’s dominant platforms. Redesigned diagram color schemes to improve clarity and engagement — a small change with outsized impact on new-hire onboarding speed. NDA restricts final diagram publication. Below are a few projects I created:

Revamped documentation structure for one of the fastest-growing Web3 developer platforms. Replaced choppy Swagger-generated output with readable, scannable docs — adding tables, section blocks, and a developer-centric template adopted across Alchemy’s writing team. Also introduced a CTA button driving free sign-ups directly from within the API reference. Below are before and after PDFs of my work.

Another solution I implemented was adding a pinch of marketing into their API docs. To entice more users on to their platform, I coded a simple call-to-action button at the top of their docs for users to get started for free.

ShipEngine.com is the leader of e-commerce shipping APIs. The project was a full rewrite of all published API conceptual help guides. These types of guides are critical to reduce onboarding of developers. My approach was to help ShipEngine lower the friction of developer onboarding. My workflow was docs-as-code writing in Markdown and Atom connected to a ShipEngine repository. I tested endpoints and received help from the developer SMEs via Slack. Some endpoint code examples were pulled from Swagger. Daily video chats with engineers about endpoint use cases helped move our project forward. Some of my ShipEngine work is below.

TowerData.com (purchased by AtData) is one of the largest email API services in the US. They hired me to rebuild their API documentation UI after testing all endpoints. Also update their SDK docs. I built a three-column UI using Ruby, Slate, and Markdown. Editing the CSS code to match the TowerData brand colors was vital to this project being a home run: https://fraud-docs.atdata.com/reference/fraud-prevention. Below are my published pages and raw Markdown draft files.

Stripe.com is one of the leading payment providers globally. I drafted new API docs for their platform users. Below are docs I wrote for Stripe.

The Epic Games Store is a world-class powerhouse with 150+ million global users. Reviewed and rewrote 120+ developer API docs for Epic’s global gaming platform with 150M+ users. Dual audience: game developers building on EOS, and end users buying from the store. Docs-as-code in Markdown throughout. Covered Auth, Lobbies, Sessions, Ecom, Player Data Storage, and Social Overlay interfaces.

Wrote API documentation for Upvest’s EU-regulated fractional share trading platform. Deep-dived into ESMA API endpoints covering EU KYC and German MiFID II identity compliance — regulatory-heavy docs requiring precision and legal fluency alongside developer clarity. Written in Markdown docs-as-code.

↳ One of the few technical writers with direct experience documenting EU financial regulation APIs, a rare and increasingly valuable niche as AI-adjacent FinTech expands into European markets.

EU KYC and German MiFID II identity compliance. Docs were written in Markdown [docs-as-code]. Slack conversations with devs solved doc blockers. Below are documents I wrote for Upvest.

 

WEXinc.com is a global payment processor of virtual credit card transactions used by Expedia.com, HotWire.com & Priceline.com. A few other thousand customers enjoy the one-time-use card numbers. I was hired by WEX Bank to document a new payments product and build a new API docs UI. I built the UI with Ruby, Slate, Markdown. The target users were bank developers in need of onboarding docs for new users.

ENS Labs is the leader managing human-readable names like alice.eth to machine-readable Ethereum addresses such as 0x742d35Cc6634C0532925a3b844Bc454e4438f44e. They exist as the ETH registrar for top-level domains to create decentralized names issued as tokens on the Ethereum Blockchain. Registration is managed by using smart-contracts. I was tasked with reviewing ENS Labs’ online developer documentation and make recommendations for improvement.

Ahana Cloud Inc, an IBM company, offers the only managed service for Presto on AWS with the vision to simplify open data lake analytics. Ahana has the vision to build the best engine for the Open Data Lakehouse used at Uber, Twitter and thousands more. Presto is the de facto standard for fast SQL processing on data lakes. I was hired by Ahana to write developer documentation for new users. Below are some of the documents I wrote for Ahana.

Tom Johnson, owner of the legendary blog IdRatherBeWriting.com, asked me to write a guest post about my portfolio development. I was honored to be part of Tom’s best-in-class API technical writing teaching site. He has been helping technical writers learn how to write API documentation since 2012. I developed many of my API doc writing skills from Tom and am a lifelong advocate of his training modules. Below is the link to my published article:

MatterLabs.io is an R&D company focused on scaling Ethereum with zero-knowledge proofs. Below is one of my rewrites for Matter Labs.

TON.org is a third-generation proof-of-stake blockchain organization. The crew at TON are fast movers in the blockchain world. TON is capable of handling millions of transactions per second. Their Toncoin is a game-changer along with their DApps and Apps. Below are some examples of my work.

Apache.org is the gold standard in big data. I was hired to write their Apache Sparke white paper on Apache Spark. It was a great project combining technical docs with a hint of marketing. The target users were analysts interested in learning about SparkSQL, Spark MLib, and SparkR. Below is the my finished version.

The Financial Industry Regulatory Authority (FINRA) is a non-profit regulatory agency that oversees brokerage firms and their registered representatives in the United States. Their regulatory bodies include the National Association of Securities Dealers (NASD) and the New York Stock Exchange (NYSE) Regulation. FINRA asked me to assess their existing documentation and make recommendations for improvement.