Fern Docs

Fern docs authoring

Write and edit documentation on a Fern site. SKILL.md is the index: follow the principles below, then read the references/ file that matches the task before writing. Don't work from this page alone when a reference exists.

Scope: this skill governs Fern docs content only — MDX pages, navigation, docs.yml and related config, snippets, changelog entries, custom components, and landing pages. It does not govern repo governance or tooling files that happen to live in the same repo, such as CLAUDE.md, AGENTS.md, STYLE-GUIDE.md, and contributor guides. Never apply the principles below — "one canonical home," "prefer editing over creating," consolidation — to those files. Leave them alone unless the user explicitly asks you to edit them.

Fern resources

Fern's configuration evolves. Look things up rather than guessing.

• Docs: https://buildwithfern.com/learn/docs/getting-started/overview.md (append .md to any docs URL for clean markdown to fetch)

• Page index: https://buildwithfern.com/learn/llms.txt

• MCP server — connect your agent to Fern's live docs and query it for any syntax or behavior you're unsure of. The endpoint works with any MCP client; for Claude Code:

  claude mcp add --transport http fern https://buildwithfern.com/learn/_mcp/server
  

Routing

Core principles

• Defer to the repo's own conventions. When a docs repo has an established pattern, voice, or structure — a CLAUDE.md, a style guide, or just the consistent practice of surrounding pages — follow it over the guidance here. This skill is the default, not an override.
• Write what the reader needs to succeed — no more. Every sentence earns its place.
• Prefer editing over creating. Search the repo for a page that already covers the topic and update it instead of adding a duplicate.
• Make minimal, precise edits. Don't rewrite a page when a paragraph fix will do.
• Push back when something seems wrong. Explain why rather than complying silently.
• Ask when unclear. Don't fill gaps with assumptions.
• Never fabricate. If you don't know a config key or behavior, look it up (MCP server or docs) or say so. Don't invent frontmatter or YAML fields.
• Cross-reference. When you mention a concept documented elsewhere, link to it so readers can find their way.
• Preserve URLs when they change. Any edit that moves, renames, or deletes a page — or changes a slug, section, or product — can change a published URL. When it does, set up redirects from the old path (see references/redirects.md) so inbound links and search rankings survive.

Links

Internal links are URL paths derived from this repo's own docs.yml and page frontmatter — not file paths on disk or relative paths. Nearly every edit touches a link, so get this right every time.

A page URL is <base-path>/<product-slug>/<rest>:

• Base path — the prefix in your docs URL (e.g. /learn, /docs; may be empty).
• Product slug — the product's slug in fern/docs.yml. Omitted for a product with no slug: (such as a default single Home product).
• <rest> — found by step 1 or step 2 below.

To find <rest>:

1. Open the target page and check its frontmatter for slug:. A frontmatter slug is absolute within the product: it is <rest> on its own, and it replaces the entire section/folder hierarchy. The section's slug does not appear. Do not walk the navigation.
2. Otherwise, walk docs.yml within the product, from section through any folders to the page. Each level contributes one slug:
   • Its explicit slug: if set.
   • Otherwise auto-derived from the display name: lowercased, spaces to hyphens, special characters stripped (so v3 (Latest) becomes v-3-latest). Auto-derivation isn't always obvious — verify, don't assume.
   • In folder-based navigation, a page's slug comes from its filename, not a display name (quick-start.mdx to quick-start).
   • Omit any level with skip-slug: true — it contributes no segment.

Example — page ./pages/ai/overview.mdx under section "AI features", in product docs, base path /learn:

• with frontmatter slug: ai-ai → /learn/docs/ai-ai (the ai-features section slug is dropped)
• with no frontmatter slug → /learn/docs/ai-features/overview (section auto-slug ai-features + page auto-slug overview)

Section slugs frequently differ from folder names, so never guess the URL from the directory layout. If you can't resolve a path from docs.yml and the page's frontmatter, say so rather than guessing.

Anchors append #heading, and only resolve for real ##/### Markdown headings — not for JSX title props like <Step title>, <Tab title>, <Accordion title>, or <Card title>.

Not internal links (leave as-is): external https:// URLs, image paths (./images/...), snippet includes (<Markdown src="/snippets/..." />), and same-page anchors (#section).

Cross-referencing

When you document new functionality — a new page, or new behavior on an existing one — related pages usually need a pointer to it, or the new content is hard to find from where readers actually start. This applies to small edits too, not just new pages.

• One canonical home. The full explanation lives on one page; every other page that touches the topic links to it instead of restating it. If you're copying more than a sentence or two onto another page, it belongs on the canonical page.

• Find the targets. Grep the docs for the feature name and one or two related keywords, then read each hit and decide whether a pointer is warranted:

  grep -rln "<feature>\|<keyword>" fern --include="*.mdx"
  

  Common targets: pages for behavior the feature affects, adjacent feature pages, and overview or landing pages.

• Use the lightest form that works: an inline link inside an existing sentence, then a <Note> for a secondary aside, then a new ## section, then a new page. Inline links and Notes add no maintenance surface; new pages and sections do.

• Phrase inline links naturally — never "See [page]." Put the link on a noun phrase already in the sentence, not a tacked-on pointer sentence. Don't wrap a lone link in a <Tip> whose only job is to host it.

  • Good: "Each request counts against your rate limit, which resets hourly."
  • Bad: "Requests are rate limited. See the rate limits reference for details."
  • Bad: a standalone <Tip> containing only "For more, see rate limits."

• Frame by function, not plumbing. Contrast what each feature does ("X decides A; Y decides B"), not that they share a config key or sit in the same directory. If the only thing linking two features is the same YAML key, it's not worth a cross-reference.