diff --git a/output/openapi/elasticsearch-openapi.json b/output/openapi/elasticsearch-openapi.json
index d077d771a7..e86f512cab 100644
--- a/output/openapi/elasticsearch-openapi.json
+++ b/output/openapi/elasticsearch-openapi.json
@@ -27965,6 +27965,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -28023,6 +28026,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -28086,6 +28092,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -28147,6 +28156,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -115210,6 +115222,16 @@
         },
         "style": "form"
       },
+      "msearch-index_": {
+        "in": "query",
+        "name": "index",
+        "description": "Comma-separated list of data streams, indices, and index aliases to use as default",
+        "deprecated": false,
+        "schema": {
+          "$ref": "#/components/schemas/_types.Indices"
+        },
+        "style": "form"
+      },
       "msearch-max_concurrent_searches": {
         "in": "query",
         "name": "max_concurrent_searches",
diff --git a/output/openapi/elasticsearch-serverless-openapi.json b/output/openapi/elasticsearch-serverless-openapi.json
index 0f216a2283..1b304f25fe 100644
--- a/output/openapi/elasticsearch-serverless-openapi.json
+++ b/output/openapi/elasticsearch-serverless-openapi.json
@@ -17187,6 +17187,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -17245,6 +17248,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -17308,6 +17314,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -17369,6 +17378,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -68944,6 +68956,16 @@
         },
         "style": "form"
       },
+      "msearch-index_": {
+        "in": "query",
+        "name": "index",
+        "description": "Comma-separated list of data streams, indices, and index aliases to use as default",
+        "deprecated": false,
+        "schema": {
+          "$ref": "#/components/schemas/_types.Indices"
+        },
+        "style": "form"
+      },
       "msearch-max_concurrent_searches": {
         "in": "query",
         "name": "max_concurrent_searches",
diff --git a/output/schema/schema.json b/output/schema/schema.json
index 3b6aa47155..6586fb032d 100644
--- a/output/schema/schema.json
+++ b/output/schema/schema.json
@@ -32808,6 +32808,18 @@
             }
           }
         },
+        {
+          "description": "Comma-separated list of data streams, indices, and index aliases to use as default",
+          "name": "index",
+          "required": false,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "Indices",
+              "namespace": "_types"
+            }
+          }
+        },
         {
           "description": "Maximum number of concurrent searches the multi search API can execute.",
           "name": "max_concurrent_searches",
@@ -32895,7 +32907,7 @@
           }
         }
       ],
-      "specLocation": "_global/msearch/MultiSearchRequest.ts#L25-L135"
+      "specLocation": "_global/msearch/MultiSearchRequest.ts#L25-L139"
     },
     {
       "kind": "type_alias",
diff --git a/output/schema/validation-errors.json b/output/schema/validation-errors.json
index 73726af55a..d9243bccb0 100644
--- a/output/schema/validation-errors.json
+++ b/output/schema/validation-errors.json
@@ -243,12 +243,6 @@
         "Request: missing json spec query parameter 'allow_no_datafeeds'"
       ],
       "response": []
-    },
-    "msearch": {
-      "request": [
-        "Request: missing json spec query parameter 'index'"
-      ],
-      "response": []
     }
   },
   "generalErrors": [
diff --git a/specification/_global/msearch/MultiSearchRequest.ts b/specification/_global/msearch/MultiSearchRequest.ts
index 96081977dd..69366b44fc 100644
--- a/specification/_global/msearch/MultiSearchRequest.ts
+++ b/specification/_global/msearch/MultiSearchRequest.ts
@@ -99,6 +99,10 @@ export interface Request extends RequestBase {
      * @server_default false
      */
     include_named_queries_score?: boolean
+    /**
+     * Comma-separated list of data streams, indices, and index aliases to use as default
+     */
+    index?: Indices
     /**
      * Maximum number of concurrent searches the multi search API can execute.
      */