# Write Docs > Authoring Fern MDX documentation pages for the Opik docs site, plus release-note and changelog routing. Use when writing or updating pages under apps/opik-documentation/documentation/fern/, drafting PR descriptions, or picking the right changelog surface. - Skill: `gabrielmoreira/write-docs` (Agent Skill) - Install (CLI): `npx skillmds@latest add gabrielmoreira/write-docs` - Raw SKILL.md: https://api.skillmd.com/api/skills/gabrielmoreira/write-docs/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Docs & Writing - Author: gabrielmoreira (https://skillmd.com/u/gabrielmoreira) - Updated: 2026-09-21 - Page: https://skillmd.com/skills/gabrielmoreira/write-docs --- # Write Docs The Opik docs site is built with [Fern](https://buildwithfern.com/) from MDX sources under `apps/opik-documentation/documentation/fern/`. There is one content surface: `fern/docs-v2/`. The old v1 surface (`fern/docs/`) was removed; every v1 URL now redirects to its Opik 2 equivalent through the `redirects:` list in `fern/docs.yml`. ## Where new pages live - Create the file at `apps/opik-documentation/documentation/fern/docs-v2/
/.mdx`. - Register it in `fern/docs.yml` under the right `section:` block in `navigation:`. - Routing is not implied by folder layout. Always check `navigation:` in `fern/docs.yml`. ## Frontmatter template Every page uses YAML frontmatter. `title` and `headline` are required; the `og:*` fields are strongly recommended for SEO/social sharing and are present on every page. Do not repeat `title` as an inline `# H1` in the body — Fern renders it from frontmatter. ```yaml --- title: Page Title headline: Page Title | Opik Documentation og:title: Page Title — Opik og:description: One-line summary used for social sharing and previews og:site_name: Opik Documentation --- ``` `subtitle: ...` is an optional field used on concept/overview pages to add a secondary line. Landing/overview pages may also set `layout: overview`. ## Style and voice Pull examples from existing pages when unsure — `fern/docs-v2/tracing/advanced/log_traces.mdx`, `fern/docs-v2/tracing/concepts.mdx`, and `fern/docs-v2/quickstart.mdx` are good anchors. - **Person:** "you" and imperative voice. Professional but approachable. - **Opening:** one or two intro sentences before the first `##` heading. No inline H1. - **Headings:** `##` for top-level sections, `###` for subsections. Never introduce an inline `#` — that collides with the frontmatter title. - **Paragraphs:** keep them short (2–4 sentences). Mix prose with bullet lists for features, options, and prerequisites. - **Page shape:** - *Concept pages* start with the *why*, then definitions. - *How-to pages* start with brief context, then the task steps. - *Overview/landing pages* lead with a short pitch and a `` of links. - **End with "## Next steps"** linking to 2–4 related pages when useful. ## Fern MDX components All examples below are taken from real pages in the repo. ### `` / `` — SDK, language, or environment choice Use when the whole section varies (not just a code block). Attach `language="..."` so Fern groups tabs across the site by the reader's last choice. ```mdx ```bash pip install opik ``` ```bash npm install opik ``` ... ``` ### `` / `` — walkthroughs For quickstarts, installs, and any sequential procedure. `title` on each `` is optional. ```mdx ```bash npx skills add comet-ml/opik-skills ``` Once the skill is installed, you can add tracing using the following prompt: ``` Instrument my agent with Opik using the /opik-instrument command. ``` ``` ### `` — multi-language code, identical surrounding prose Prefer this over `` when only the code varies. ```mdx ```python title="Python" import opik opik.configure() ``` ```ts title="Typescript" import Opik from "opik"; const client = new Opik(); ``` ``` ### `` / `` — landing and integration grids ```mdx } iconPosition="left"/> } iconPosition="left"/> } iconPosition="left"/> ``` ### `` / `` — FAQs and expandable advanced topics ```mdx The Agent Optimizer provides a unified interface... ``` ### `` — image wrapper (always wrap images) ```mdx ``` ### Callouts: ``, ``, ``, ``, `` Pick by intent, not aesthetics: - **``** — cross-references, shortcuts, "If you're just getting started, see..." - **``** — clarifications and recommendations that aren't risky - **``** — breaking changes, footguns, prerequisites that will break things - **``** — informational, interchangeable with `` in practice - **``** — catch-all when none of the above fits ```mdx If you are just getting started with Opik, we recommend first checking out the [Quickstart](/quickstart) guide. Note that the authorization header value does not include the `Bearer ` prefix. ``` ## Code examples - Use `` for multi-language blocks; use `` when surrounding prose also varies. - Install commands are inline bash blocks (`pip install opik`, `npm install opik`). - There is no snippet-include system. All code is written inline in MDX. - **Use placeholders for credentials:** ``, ``, ``. Never commit real keys. ## Images - Store under `apps/opik-documentation/documentation/fern/img/
/...`. - Reference from MDX as `/img/
/.png` (path is rooted at the docs base). - **Never** put new assets in `static/img/` — that folder is legacy and only kept for external integrations. - Always wrap with ``. Captions are not a repo convention. ## Cross-links Root-relative, slug-based paths only (`/section/page`). - **Never** link internal docs pages with full `https://www.comet.com/docs/opik/...` URLs. Full URLs bypass the Fern preview build, and they 404 in the link checker when the target page ships in the same PR. Use the root-relative slug path instead. - No file-relative paths (`../foo`) either. - Build the path from `navigation:` in `fern/docs.yml`, including every nested `section:` slug. Example: the "Manage datasets" page sits inside an `advanced` section, so the path is `/evaluation/advanced/manage_datasets`, not `/evaluation/manage_datasets`. ```mdx [Python SDK](/reference/python-sdk/overview) [Log traces](/tracing/advanced/log_traces) [Integrations overview](/integrations/overview) ``` In-page anchors use the heading slug: `[Concepts](#concepts)`. ## Routing: adding a page to `docs.yml` Add a page entry under the correct `section:` in `navigation:` (keep the YAML at 2-space indent): ```yaml - page: Page Title path: ./docs-v2/section/page-name.mdx slug: page-name ``` ## File naming - Kebab-case for new files: `getting-started.mdx`, `log-traces.mdx`. - When editing an existing section that uses snake_case, match neighbors rather than renaming. Renames require redirect entries in `docs.yml`. ## Local verification ```bash cd apps/opik-documentation/documentation npm install # first time only npm run dev # live-reload preview ``` Open the rendered page and confirm: - Frontmatter renders (title shows, no stray H1 in body). - Every MDX component resolves (no raw `` tags visible). - Every link works (no 404s, no `Broken link` warnings in the terminal). - Images load. ## Changelog routing Pick the changelog target by scope — do not default everything to one surface. - `apps/opik-documentation/documentation/fern/docs-v2/self-host/changelog.mdx` — self-hosted deployment changelog shown at `/docs/opik/self-host/changelog`. Breaking, critical, or security-impacting changes only. (The former repo-root `CHANGELOG.md` was removed; its content lives on this page now.) - `apps/opik-documentation/documentation/fern/docs-v2/changelog/*.mdx` — general product release notes shown at `/docs/opik/changelog`. One dated `.mdx` per entry. - `apps/opik-documentation/documentation/fern/docs-v2/development/optimization-runs/changelog.mdx` — Agent Optimizer version updates (e.g. `sdks/opik_optimizer` releases like `3.1.0`). - Liquibase `changelog.xml` files are migration manifests, not user-facing release notes. Do not put prose there. - When unsure, confirm the surface from `fern/docs.yml` before editing. ### Changelog entry template ```markdown ### [VERSION] - [DATE] #### New Features - **Feature Name**: Brief description #### Improvements - **Improvement**: What changed and why #### Bug Fixes - **Fix**: What was broken (#issue) #### Breaking Changes - **Change**: What breaks, migration steps ``` ## Feature documentation checklist When documenting a new feature, cover: - **User impact** — What capability does this add? How do users access it? - **Technical changes** — API endpoints and params, SDK methods, config or env vars, migrations. - **Breaking changes** — What breaks and the migration path, if any. Keep it user-facing: avoid implementation detail unless it affects how someone uses the feature. ## PR description template Use the repository template at `.github/pull_request_template.md` — read the FULL file before drafting (the required sections continue past the first screen). CI (`.github/workflows/pr-lint.yml`) fails any PR whose description is missing one of these exact headings: - `## Details` - `## Change checklist` - `## Issues` - `## Testing` - `## Documentation` Also fill in the template's `## AI-WATERMARK` section (yes/no; if yes: Tools, Model(s), Scope, Human verification). Never invent a different structure such as `## Summary` / `## Test Plan`. A section that does not apply gets `N/A` — never delete a heading. ### `## Details` — style Write what changes for a user. A reviewer reads the diff for the code; this section tells them what is different when they use the product. - **Short.** Most PRs need 3–10 bullets. If it runs longer, the section is doing the diff's job — cut it. - **Bullets, not prose paragraphs.** One behavior per bullet. Nest one level for sub-cases. - **Authoritative.** State what happens: "The run is scored once." Not "This should now mean that the run will be scored once." - **No fluff.** No motivation paragraph, no "this PR …", no approach summary, no benefits list, no restating the diff. - **Observable behavior first.** What the UI shows, what the API returns, what gets scored, stored or logged. Name a class, method or file only when the behavior makes no sense without it. Pick the shape that fits the change — do not force one: - **Before / After bullet lists** when a behavior changed and the contrast is the point. - **A flat bullet list** for a new capability, where there is no "before". - **One or two lines** when users cannot see the change (refactor, dependency bump) — say what is unchanged and what improved, then stop. ## Internationalized READMEs `readme_CN.md`, `readme_ES.md`, `readme_FR.md`, `readme_DE.md` are AI machine-translated from the English `README.md`. - Each non-English README has a blockquote notice at the top warning that it is AI-translated and welcoming improvements. Keep it. - When the English README changes meaningfully, re-translate the affected files. Do not hand-edit translated READMEs for content changes — update the English source and re-translate. ## Forbidden and discouraged - No real API keys, tokens, or workspace IDs in examples — always placeholders. - Do not put new images outside `fern/img/`. `static/img/` is legacy-only and cannot be deleted because of external integrations. - Do not infer URL paths from folder layout — always consult `navigation:` in `fern/docs.yml`. - Do not add an inline `# H1` inside the body — the frontmatter `title` already provides it. ## Key files - `apps/opik-documentation/documentation/fern/docs.yml` — site config: tabs, `navigation:` routing, and `redirects:`. Edit `navigation:` when adding pages. - `apps/opik-documentation/documentation/fern/docs-v2/` — target directory for new pages. - `apps/opik-documentation/documentation/fern/img/` — image storage. - `apps/opik-documentation/AGENTS.md` — docs-module contribution rules. - `.github/release-drafter.yml` — release notes template.