diff --git a/docs/tools-custom/authentication.md b/docs/tools-custom/authentication.md
index 4656c92cf1..c161ac5e0f 100644
--- a/docs/tools-custom/authentication.md
+++ b/docs/tools-custom/authentication.md
@@ -131,6 +131,10 @@ specific interactive process with your ***Agent Client*** application.
 *   **SERVICE\_ACCOUNT:** Provides Google Cloud Service Account credentials as a
     JSON key or Application Default Credentials. This type typically exchanges a
     Bearer token.
+*   **GCP_AUTH_PROVIDER:** Leverages the GCP Agent Identity integration
+    ([`GcpAuthProviderScheme`](/integrations/agent-identity)) to automatically
+    handle 2-legged and 3-legged OAuth flows using Google Cloud's IAM
+    Connector Credentials service.
 
 ## Tools and integrations quick guide
 
@@ -803,4 +807,4 @@ except Exception as e:
                required:
                   - code
                   - message
-         ```
+         ```
\ No newline at end of file