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Document SSO token retrieval and bearer auth for the MCP server #6566

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Document SSO token retrieval and bearer auth for the MCP server #6566

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12 changes: 11 additions & 1 deletion fern/products/docs/pages/ai/mcp-server.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,16 @@ Exchange your credentials for a JWT. The endpoint depends on how your site authe

Extract the `fern_token` value from the `Set-Cookie` header in the response.
</Tab>
<Tab title="SSO">
Log in to your docs site in a browser, then request the whoami endpoint from the same browser. It reads the session cookie set at login and returns the token:

```
https://docs.example.com/api/fern-docs/whoami
→ { "fern_token": "eyJ...", "user_info": { ... } }
```

The session cookie is `httpOnly`, so the token isn't readable from client-side JavaScript.
</Tab>
</Tabs>
</Step>

Expand All @@ -78,7 +88,7 @@ claude mcp add --transport http \
fern_mcp_docs.example.com https://docs.example.com/_mcp/server
```

For Cursor, VS Code, and other clients, add `FERN_TOKEN: <jwt>` to the `headers` field in your MCP server configuration if the client supports custom headers.
For Cursor, VS Code, and other clients, add `FERN_TOKEN: <jwt>` to the `headers` field in your MCP server configuration if the client supports custom headers. Clients that only send bearer tokens can pass the JWT as `Authorization: Bearer <jwt>` instead.
</Step>
</Steps>

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7 changes: 7 additions & 0 deletions fern/products/docs/pages/changelog/2026-08-07.mdx
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@@ -0,0 +1,7 @@
## Authenticate the MCP server with a bearer token

<ChangelogTags>mcp, authentication</ChangelogTags>

The MCP server on authenticated sites now accepts the docs JWT as `Authorization: Bearer <jwt>`, in addition to the `FERN_TOKEN` header, so MCP clients that only send bearer tokens can read authenticated content. On SSO sites, retrieve the token from `/api/fern-docs/whoami` after logging in to your docs site in a browser.

<Button intent="none" outlined rightIcon="arrow-right" href="/learn/docs/ai/mcp-server#authenticated-sites">Read the docs</Button>
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