diff --git a/api-ref/source/v3-ext/federation/auth/auth.inc b/api-ref/source/v3-ext/federation/auth/auth.inc
index 8dec196074..a76af83a25 100644
--- a/api-ref/source/v3-ext/federation/auth/auth.inc
+++ b/api-ref/source/v3-ext/federation/auth/auth.inc
@@ -40,6 +40,7 @@ Response
 
 .. rest_parameters:: federation/auth/parameters.yaml
 
+   - X-Subject-Token: X-Subject-Token
    - token: unscoped_token
 
 Response Example
@@ -81,6 +82,7 @@ Response
 
 .. rest_parameters:: federation/auth/parameters.yaml
 
+   - X-Subject-Token: X-Subject-Token
    - token: scoped_token
 
 Response Example
diff --git a/api-ref/source/v3-ext/federation/auth/parameters.yaml b/api-ref/source/v3-ext/federation/auth/parameters.yaml
index f187af0765..e07aa3dfcc 100644
--- a/api-ref/source/v3-ext/federation/auth/parameters.yaml
+++ b/api-ref/source/v3-ext/federation/auth/parameters.yaml
@@ -1,5 +1,14 @@
 # variables in header
 
+X-Subject-Token:
+  description: |
+    The authentication token. An authentication
+    response returns the token ID in this header rather than in the
+    response body.
+  in: header
+  required: true
+  type: string
+
 # variables in path
 
 idp_id: