The guides
Short guides on how AI actually behaves and what it means for personal details and for money work. Document Substrate is the system built around those answers: it reads a pile of documents, hides the personal details before they go anywhere, and turns the pile into answers and finished workpapers that show their working. Plain words, one picture per idea.
Start here
The ideas underneath. Read these first and the rest of the collection reads easily.
Five ideas that explain almost everything: messages, tokens, the context window, tools, and agents.
llm-fundamentals/eli5-llm-fundamentals.htmlAnswering from your own documents: two kinds of search, a filing system for meaning, the merge that combines them, and the loop that turns it into a chat.
rag/eli5-rag.htmlPrompts, skills and tools: the note that says how to behave, the recipes it opens when a job calls for them, the hands it borrows to act, and which to reach for.
prompts-skills-tools/eli5-prompts-skills-tools.htmlWhat counts as a personal detail, where it goes wrong, and the two protections people mix up — a disguise and a promise.
pii/eli5-pii.htmlWhy an AI that gives different answers to the same question can still be trusted with money work: where the errors come from, and the checks that keep the numbers exact.
finance-determinism/eli5-finance-determinism.htmlFive words people mix up: information, knowledge, intelligence, judgment and expertise. What each one is, how they differ, and how they build on each other.
expertise/eli5-expertise.htmlDocument Substrate
Those ideas put to work: the system that turns a pile of documents into answers and finished workpapers.
The whole system explained simply, in eight big pictures — upload to workpaper, plus the practice manual and the safety gates.
how-it-works/eli5-how-it-works.htmlThe architecture explained simply: the pieces, the three shelves of memory, a question’s journey.
architecture/eli5-architecture.htmlThe privacy design explained simply: the promise, the three nets, the vault, and where real details do travel.
privacy/eli5-privacy.htmlTeaching the system a new checking job, explained simply.
creating-a-workflow/eli5-creating-a-workflow.htmlHow answers stay good: the quality loop and the exam books, explained simply.
evals/eli5-evals.htmlBuilding a check from a sentence, teaching it a new document type, the record of decisions, and what runs on its own, explained simply.
definitions/eli5-definitions.htmlHow staff in an accounting practice move from typing figures to reviewing and advising, and what the Document Substrate takes over at each stage.
six-stages/eli5-six-stages.html