diff --git a/CHANGELOG.md b/CHANGELOG.md
index f82dee799..73397cbae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,12 +8,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- Submission endpoint update #371
+  - Adds mandatory query parameter `folder` for submit endpoint POST 
+  - On actions add and modify object is added or updated to folder(submission) where it belongs with it's accession ID, schema, submission type, title and filename
+  - Adds metax integration to submit endpoint
 - Integration with Metax service #356
   - Adds new local container for testing against mocked Metax API
   - Introduces new env vars: METAX_USER, METAX_PASS, METAX_URL
   - Adds new key metaxIdentifier to Study and Dataset collections containing metax id returned from Metax API
   - Adds new handler MetaxServiceHandler to take care of mapping Submitter metadata to Metax metadata and to connect to Metax API
 - Add patching of folders after object save and update operations #354
+  - Adds mandatory query parameter `folder` for objects endpoint POST 
   - Object is added or updated to folder(submission) where it belongs with it's accession ID, schema, submission type, title and filename in the case of CSV and XML upload
   - Adds configuration for mypy linting to VScode devcontainer setup
 - Templates API #256
@@ -46,7 +51,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - multilevel add patch objects to support `/extraInfo/datasetIdentifiers/-` which needs dot notation for mongodb to work e.g. `extraInfo.datasetIdentifiers` #332
 
 ### Changed
-
 - Refactor auth.py package by removing custom OIDC code and replacing it with https://github.com/IdentityPython/JWTConnect-Python-OidcRP. #315
   - New mandatory ENV `OIDC_URL`
   - New optional ENVs `OIDC_SCOPE`, `AUTH_METHOD`
diff --git a/docs/specification.yml b/docs/specification.yml
index 8860160c9..12869a181 100644
--- a/docs/specification.yml
+++ b/docs/specification.yml
@@ -21,6 +21,14 @@ paths:
       tags:
         - Submission
       summary: XML submission endpoint, will also trigger validation.
+      parameters:
+        - name: folder
+          in: query
+          schema:
+            type: string
+          description: The folder ID where object belongs to.
+          required: true
+          example: "folder=12345"
       requestBody:
         content:
           multipart/form-data:
@@ -293,11 +301,6 @@ paths:
         - Submission
       summary: Submit data to a specific schema
       parameters:
-        - in: query
-          name: folder
-          schema:
-            type: string
-          description: The folder ID where object belongs to.
         - name: schema
           in: path
           description: Name of the Metadata schema.
diff --git a/metadata_backend/api/handlers/submission.py b/metadata_backend/api/handlers/submission.py
index ac461ef58..c0a935d15 100644
--- a/metadata_backend/api/handlers/submission.py
+++ b/metadata_backend/api/handlers/submission.py
@@ -121,10 +121,11 @@ async def _execute_action(self, req: Request, schema: str, content: str, action:
 
         Only "add/modify/validate" actions are supported.
 
+        :param req: Multipart POST request
         :param schema: Schema type of the object in question
         :param content: Metadata object referred to in submission
-        :param db_client: Database client for database operations
         :param action: Type of action to be done
+        :param filename: Name of file being processed
         :raises: HTTPBadRequest if an incorrect or non-supported action is called
         :returns: Dict containing specific action that was completed
         """
@@ -144,14 +145,12 @@ async def _execute_action(self, req: Request, schema: str, content: str, action:
             raise web.HTTPBadRequest(reason=reason)
 
     async def _execute_action_add(self, req: Request, schema: str, content: str, filename: str) -> Dict:
-        """Complete the command in the action set of the submission file.
-
-        Only "add/modify/validate" actions are supported.
+        """Complete the add action.
 
+        :param req: Multipart POST request
         :param schema: Schema type of the object in question
         :param content: Metadata object referred to in submission
-        :param db_client: Database client for database operations
-        :param action: Type of action to be done
+        :param filename: Name of file being processed
         :raises: HTTPBadRequest if an incorrect or non-supported action is called
         :returns: Dict containing specific action that was completed
         """
@@ -193,14 +192,12 @@ async def _execute_action_add(self, req: Request, schema: str, content: str, fil
         return result
 
     async def _execute_action_modify(self, req: Request, schema: str, content: str, filename: str) -> Dict:
-        """Complete the command in the action set of the submission file.
-
-        Only "add/modify/validate" actions are supported.
+        """Complete the modify action.
 
+        :param req: Multipart POST request
         :param schema: Schema type of the object in question
         :param content: Metadata object referred to in submission
-        :param db_client: Database client for database operations
-        :param action: Type of action to be done
+        :param filename: Name of file being processed
         :raises: HTTPBadRequest if an incorrect or non-supported action is called
         :returns: Dict containing specific action that was completed
         """