docs: add per-page directives section for agents config

fern/products/docs/pages/ai/llms-txt.mdx

@@ -145,6 +145,15 @@ To authenticate your requests, include your API key in the header.
 </Accordion>
 </AccordionGroup>
 
+## Per-page directives
+
+Use the [`agents` key in `docs.yml`](/learn/docs/configuration/site-level-settings#agents-configuration) to prepend a short instruction to AI agents when they fetch the Markdown version of a page, so they can discover and navigate your full docs. The directive is injected after the frontmatter metadata section but before the page body, so agents see it first even if they truncate the rest of the page. It applies to individual page Markdown (`.md`/`.mdx` URLs) and to each page section within `llms-full.txt`. Human-facing documentation is unaffected.
+
+```yaml docs.yml
+agents:
+  page-directive: "For a complete page index, fetch https://docs.example.com/llms.txt"
+```
+
 ## Analytics and monitoring
 
 The [Fern Dashboard](https://dashboard.buildwithfern.com/) provides comprehensive analytics for `llms.txt` usage including:

fern/products/docs/pages/changelog/2026-04-02.mdx

@@ -0,0 +1,14 @@
+---
+tags: ["ai", "configuration", "docs.yml"]
+---
+
+## Per-page directives in llms.txt
+
+You can now add a directive that is automatically prepended to every page when it's served to AI agents — both individual Markdown page URLs and each page section within `llms-full.txt`. The directive is only visible to agents requesting Markdown; human-facing documentation is unaffected.
+
+```yaml docs.yml
+agents:
+  page-directive: "For a complete page index, fetch https://docs.example.com/llms.txt"
+```
+
+<Button intent="none" outlined rightIcon="arrow-right" href="/learn/docs/ai-features/llms-txt#per-page-directives">Read the docs</Button>

fern/products/docs/pages/customization/site-level-settings.mdx

@@ -1002,6 +1002,19 @@ Specify [Ask Fern](/learn/ask-fern/getting-started/what-is-ask-fern) to control
 
 <Markdown src="/snippets/ask-fern-config.mdx" />
 
+## Agents configuration
+
+Configure directives that are prepended to every page when it's [served to AI agents](/learn/docs/ai-features/llms-txt#per-page-directives).
+
+```yaml docs.yml
+agents:
+  page-directive: "For a complete page index, fetch https://docs.example.com/llms.txt"
+```
+
+<ParamField path="agents.page-directive" type="string" required={false} toc={true}>
+  Text prepended to each page's Markdown output when served to AI agents. The directive is injected after the frontmatter metadata section but before the page body. Human-facing documentation is unaffected.
+</ParamField>
+
 ## AI examples configuration
 
 Configure [AI-generated examples](/learn/docs/ai-features/ai-examples) for your API Reference pages.

fern/products/docs/pages/developer-tools/view-markdown.mdx

@@ -17,3 +17,5 @@ Displaying the page's Markdown helps with troubleshooting layout problems and ma
 </Frame>
 
 Fern also bundles your entire site's Markdown into [`llms.txt` and `llms-full.txt`](/learn/docs/ai-features/llms-txt) files for AI consumption. These files use the same underlying Markdown you see when viewing a single page and respect the same `<llms-only>` and `<llms-ignore>` content controls.
+
+You can configure a [per-page directive](/learn/docs/ai-features/llms-txt#per-page-directives) that is automatically prepended to every page's Markdown output when served to AI agents. This is useful for pointing agents to your `llms.txt` index so they can discover the rest of your docs. The directive is only visible to agents — human-facing documentation is unaffected.