diff --git a/output/openapi/elasticsearch-openapi.json b/output/openapi/elasticsearch-openapi.json
index 0a2b13d75f..27e646f606 100644
--- a/output/openapi/elasticsearch-openapi.json
+++ b/output/openapi/elasticsearch-openapi.json
@@ -31883,6 +31883,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -31947,6 +31950,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -32016,6 +32022,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -32083,6 +32092,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -122122,6 +122134,16 @@
         },
         "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": {
+          "$ref": "#/components/schemas/_types.Indices"
+        },
+        "style": "form"
+      },
       "msearch-max_concurrent_searches": {
         "in": "query",
         "name": "max_concurrent_searches",
diff --git a/output/openapi/elasticsearch-serverless-openapi.json b/output/openapi/elasticsearch-serverless-openapi.json
index 7f2721e5c0..f582a635a5 100644
--- a/output/openapi/elasticsearch-serverless-openapi.json
+++ b/output/openapi/elasticsearch-serverless-openapi.json
@@ -19629,6 +19629,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -19693,6 +19696,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -19762,6 +19768,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -19829,6 +19838,9 @@
           {
             "$ref": "#/components/parameters/msearch-include_named_queries_score"
           },
+          {
+            "$ref": "#/components/parameters/msearch-index_"
+          },
           {
             "$ref": "#/components/parameters/msearch-max_concurrent_searches"
           },
@@ -73084,6 +73096,16 @@
         },
         "style": "form"
       },
+      "msearch-index_": {
+        "in": "query",
+        "name": "index",
+        "description": "Comma-separated list of data streams, indices, and index aliases to use as default",
+        "deprecated": false,
+        "schema": {
+          "$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 a094ebd252..683eea2fc6 100644
--- a/output/schema/schema.json
+++ b/output/schema/schema.json
@@ -33143,6 +33143,18 @@
             }
           }
         },
+        {
+          "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.\nDefaults to `max(1, (# of data nodes * min(search thread pool size, 10)))`.",
           "name": "max_concurrent_searches",
@@ -33230,7 +33242,7 @@
           }
         }
       ],
-      "specLocation": "_global/msearch/MultiSearchRequest.ts#L25-L136"
+      "specLocation": "_global/msearch/MultiSearchRequest.ts#L25-L140"
     },
     {
       "kind": "type_alias",
diff --git a/output/schema/validation-errors.json b/output/schema/validation-errors.json
index 5cc54d1f6a..f6fab219e8 100644
--- a/output/schema/validation-errors.json
+++ b/output/schema/validation-errors.json
@@ -1,11 +1,4 @@
 {
-  "endpointErrors": {
-    "msearch": {
-      "request": [
-        "Request: missing json spec query parameter 'index'"
-      ],
-      "response": []
-    }
-  },
+  "endpointErrors": {},
   "generalErrors": []
 }
\ No newline at end of file
diff --git a/specification/_global/msearch/MultiSearchRequest.ts b/specification/_global/msearch/MultiSearchRequest.ts
index c448fb7181..4888c0666d 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.
      * Defaults to `max(1, (# of data nodes * min(search thread pool size, 10)))`.