diff --git a/apis/builder/validators.yaml b/apis/builder/validators.yaml
index f6628589..8326fa19 100644
--- a/apis/builder/validators.yaml
+++ b/apis/builder/validators.yaml
@@ -21,7 +21,10 @@ post:
         schema:
           type: array
           items:
-              $ref: "../../builder-oapi.yaml#/components/schemas/SignedValidatorRegistration"
+            $ref: "../../builder-oapi.yaml#/components/schemas/SignedValidatorRegistration"
+      application/octet-stream:
+        schema:
+          description: "SSZ serialized `List[SignedValidatorRegistrationV1, VALIDATOR_REGISTRY_LIMIT]` bytes. Use content type header to indicate that SSZ data is contained in the request body."
   responses:
     "200":
       description: Success response.
@@ -34,5 +37,7 @@ post:
           example:
             code: 400
             message: "unknown validator"
+    "415":
+      $ref: "../../builder-oapi.yaml#/components/responses/UnsupportedMediaType"
     "500":
       $ref: "../../builder-oapi.yaml#/components/responses/InternalError"