UX Writing and Docs Rules

UX Writing & Docs

User-visible text is product behavior and carries the same quality bar as code. Every rule below is distilled from a real defect caught in review, and keeps its counter-example because the reasoning is the point. When in doubt, re-read the output as the user who just hit the problem.

Status output & diagnostics

• Report effective values, not stored ones. A status display answers "what will happen when I run this", so resolve values exactly the way the runtime does, including environment variables and layered config. Counter-example: a config viewer printed "API key set: no" while an env var held the key the next run would actually use.
• Diagnostics must stay truthful under failure. When one config layer fails to load, fall back to the most complete state that still loads, never to blank defaults. A diagnostic that misreports is worse than one that aborts. Counter-example: a broken project-level config made a doctor command check blank defaults and report a missing API key that was in fact configured; the fake failure buried the real one.
• Show deltas, not dumps. A health/diagnostic command lists what deviates and who set it; the exhaustive listing belongs to the dedicated inspect command. Don't make one command duplicate another's job. Counter-example: a doctor check printed fifteen "field: origin" lines, most of them saying "global". One line naming the two real overrides replaced the block.
• Annotate at the granularity of the claim. If one sub-part of a composite value has a different source or state, say it on the sub-part; don't relabel the whole. Counter-example: an env-injected API key relabeled an entire endpoint block "(environment)" although its URL and model came from a file. The fix was "key from env", with the block label unchanged.
• Re-read neighboring labels after adding metadata. New suffixes collide with existing value labels. Counter-example: "Embedding dimensions: default (default)", fixed by renaming the value "auto".
• Machine-readable output is a contract. Porcelain/TSV/JSON output never gains decoration, notices, or annotations; informational text goes to stderr or the human-format path. Absence is part of the contract, so write the negative test ("(project)" not in stdout).
• Never truncate the payload. Paths, IDs, and URLs in diagnostics must survive narrow terminals un-ellipsized (disable auto-wrap/crop for those lines); a truncated path cannot be copied into the next command.

Error messages

Every error answers three questions: what happened, where, and what to do now. The strongest pattern: name the offending file or input, list the rejected fields, list the allowed fields, and say where the rejected setting belongs instead. Fail loudly rather than degrade silently; when catching an exception purely to suppress a traceback, keep the message intact.

Documentation

• Each document has one responsibility, and it decides what belongs. A page is a durable contract, a proposal, an investigation, a TODO, a dated work order, or a runbook — one of them, not several. Naming that first is what makes a canonical home decidable: a fact lives on the page whose job it is, and every other surface reaches it through a single specific link instead of a partial retelling on each page that happens to touch it. When two pages both claim to be the detailed spec, the broader responsibility keeps the shared rules and the narrower keeps only what its own surface adds. Counter-example: an implementation plan stayed the de-facto spec after shipping, so the rules lived half there and half in the architecture doc; folding the stable rules into the contract and leaving the sequence in git history left one page to trust.
• Rationale is a genre of its own. A how-to answers what to run, a reference answers what exists, and why-it-was-built-this-way belongs to a design record, an ADR, or the pull request that decided it. Answering the design question inside a usage page pushes the steps the reader came for below the fold, and the argument is also the part that rots first: the implementation moves on and only the guide still defends the old choice. An explanation produced because someone asked once belongs in that answer, not in a permanent page. Counter-example: a setup guide spent its second paragraph on why this queue was chosen over two others; the queue was replaced a release later and the paragraph outlived it.
• One canonical home per fact. Details that change together (field lists, precedence chains, supported values) live in exactly one document; every other mention links to it. Legitimate copies: artifacts distributed standalone (a bundled skill file that ships without the repo), and genuinely surface-specific nuance. Counter-example: a seven-field allowlist pasted into five docs.
• Restating and linking is a bug, not thoroughness. If a section duplicates the canonical content and then ends with "see X for the full contract", it already is the full contract. Delete the restatement; keep the link and whatever is specific to this surface.
• Prefer the smallest sufficient edit. When revising existing text, preserve unaffected wording, structure, and rationale. Remove genuine duplication, but do not rewrite neighboring prose or compress away useful distinctions without a reason. Counter-example: changing one mandatory workflow into an optional one rewrote several surrounding sections, then over-corrected by removing useful context; a few local edits were enough.
• Insertion respects adjacency. Before adding a section, check what the surrounding paragraphs attach to. Counter-example: a new section landed between a flags table and its output-format footnote, orphaning the footnote in the wrong chapter.
• Adjectives need evidence. "Recommended", "faster", "better" come from your own benchmarks, not optimism. Counter-example: a feature was about to ship commented "# recommended" while the project's own eval showed it losing to the default on strong models. It shipped as "optional".
• Every README section has one job. Positioning sections ("Why X?") don't accumulate feature bullets; quick-starts don't explain architecture. A README stays lean and links into the docs; detail accumulating there usually means it left its canonical home.
• Order a page by what the reader needs first, and split when it stops being one task. Open with scope and the authoritative entry points, then the common rules and the main path, and only then exceptions, recovery, and change checks. An overview layer summarizes stable semantics and links down; it does not carry field tables, full payloads, or current numbers to buy self-containment. When a page starts demanding that the reader understand several unrelated tasks, or whole chapters serve only two maintainers, that is the signal to split it — and the split leaves behind one line of purpose plus the link, never a second copy of the fact. Counter-example: a getting-started page opened with the full option reference, so the three commands a first-time reader needed sat two screens below it.
• Reminders name the most-forgotten item only. A guideline that enumerates every artifact reads as noise and gets skipped whole. "Update whichever docs the change affects; the bundled skill is the easiest to forget" beats a list of six file types.

Facts that go stale

Docs are edited on a human cadence, while some facts change on every commit, deploy, or restart. Writing one of those into a long-lived page is not a maintenance burden, it is a defect on a delay: the page turns wrong on its own, and nothing fails when it does. Record where the current answer is read, not the answer. This is "report effective values, not stored ones" applied to prose.

• Never snapshot a value that moves faster than the doc. Long-lived pages (README, architecture notes, runbooks, domain docs) carry the stable material: intent, invariants, boundaries, procedures, failure handling. Version and protocol numbers, image tags, build IDs, deployed commit hashes, object and migration counts, expiry dates, and "currently live / not yet shipped" claims all change without anyone re-reading the page that repeats them. Those belong in a changelog, in git history, or on the release ticket, where carrying a date is the point. The rule forbids the hand-maintained second copy, not the table: when a page genuinely has to show current values, generate it from the authoritative source at build time so it cannot drift silently. Counter-example: a runbook opened with "production currently runs 2.3.1"; four releases later an on-call engineer trusted the line and worked through the wrong version's changelog.
• A pointer names a symbol, not a repository. The canonical home for a fact is often code rather than a doc, and then the doc's job is to say where to read it instead of copying the value or the whole field table. Make the pointer land: a specific file plus a searchable symbol, function, data key, or heading. "See the source", a repo-root link, or a directory leaves the reader to re-derive what the sentence promised. If no single symbol owns the fact, that is a code problem surfacing as a doc problem; fix the boundary instead of papering over it with a copied table. A directory is a fair target in two cases only: the fact emerges from an ordered set with no single-file truth (migrations replayed in sequence), or the directory is a catalog some loader enumerates (locales, plugins, maps). Both still owe a searchable selection key — the naming convention, the loader function, the object name. Counter-example: "protocol versions are defined in the networking layer" sent every reader grepping six files, and became a link to PROTOCOL_VERSION in net/constants.py.
• A doc cannot observe the runtime. The repository answers how a commit is meant to behave; only the running system knows which commit is live, what is healthy, and which artifact is being served. Docs record the command or console that answers those questions, never the answer, and never promote merged code to "deployed". A successful deploy report is evidence on that release's ticket; copying it into a doc converts a one-time result into a standing hand-sync obligation. Counter-example: a "current environment" table listing service versions was updated by hand after every deploy, until the deploy where it wasn't, and nothing in CI could notice.