diff --git a/custom-backend-docs/README.md b/custom-backend-docs/README.md
index 40b6b1b..ceaf77f 100644
--- a/custom-backend-docs/README.md
+++ b/custom-backend-docs/README.md
@@ -38,7 +38,7 @@ Yes, for custom backend that wanna stay forward-backward compatible. This will r
 
 ---
 
-========== COMING SOON ==========
+## Table Of Content
 
-Further infomation about the api interface will be avaliable soon.
+- [v0](specs/v0/spec.md)
 
diff --git a/custom-backend-docs/specs/v0/spec.md b/custom-backend-docs/specs/v0/spec.md
new file mode 100644
index 0000000..c43ea2e
--- /dev/null
+++ b/custom-backend-docs/specs/v0/spec.md
@@ -0,0 +1,207 @@
+# v0 Specification
+
+This `v0` specification is only for prototyping & is not intended to be treated as production ready in any manner...
+
+all the route in v0 spec should be prefix with `{BASE_URL}/v0/`.
+
+
+# Routes
+
+## Passwords
+
+### POST /passwords
+
+It is use by passcodes app to post the data of single password entity that needs to be saved by server.
+
+**Responsible**:
+
+for saving the password entity on backend, this should return the saved password entity's id. 
+
+**Request**:
+
+will be a post request with just a body.
+
+```json
+{
+    "domain": "string",
+	"username": "string",
+	"password": "string",
+	"notes": "string"
+}
+```
+
+**Responses**:
+
+- 201 CREATED
+    
+    In ideal cases the api should, return the id in response body.
+    
+    ```json
+    {
+        "id": "int"
+        "domain": "string",
+	    "username": "string",
+	    "password": "string",
+	    "notes": "string",
+        "created-at": "string",
+        "updated-at": "string",
+    },
+    ```
+
+**Note**:
+
+We don't care for duplicates atleast for now. We in next specification version will provide a way, 
+To let you send a specific status code when there is duplicates. It would be probably 400 BAD REQUEST.
+
+---
+
+### GET /passwords
+
+It is use by passcodes app to get all the passwords previously saved by user.
+
+**Responsible**:
+
+for retriving all the passwords previously saved by user from backend. 
+
+**Request**: 
+
+will be a GET request with no query, path or any other parameters.
+
+**Responses**:
+
+- 200 OK
+    
+    In ideal cases the api should, return all the passwords.
+    
+    ```json
+    [
+        {
+            "id": "int",
+            "domain": "string",
+            "username": "string",
+            "passwords": "string",
+            "notes": "string",
+            "created-at": "string",
+            "updated-at": "string",
+        },
+        ....
+    ]
+    ```
+
+**Note**:
+
+The authentication, pagination or query parameters based filter is not required currently. 
+As this api specification is just for prototyping, but we will later add this features... 
+If you can add there support from now itself then its good. 
+but be sure that our app may still expect this api specification, without any extra fancy feaures.
+
+---
+
+### GET /passwords/:id
+
+It is used by passcodes app to retrive single passwords entity.
+
+**Responsible**: 
+
+for getting the a password entity by its id.
+
+**Request**:
+
+will be a get request with a `:id` as a path parameter.
+
+**Responses**:
+
+- 200 OK
+
+    In ideal cases the api should, return the password entity in response body.
+
+    ```json
+    {
+        "id": "int",
+        "domain": "string",
+        "username": "string",
+        "passwords": "string",
+        "notes": "string",
+        "created-at": "string",
+        "updated-at": "string",
+    },
+    ```
+
+
+- 404 NOT FOUND
+
+    In cases where resource(password) not exist, the api should return 404.
+
+**Note**:
+
+...
+
+---
+
+### PUT /passwords/:id
+
+It is used by passcodes app to update the data of a specific password entity.
+
+**Responsible**:
+
+for updating the password entity by its id.
+
+**Request**:
+
+will be a put request with a `:id` as a path parameter.
+
+**Responses**:
+
+- 200 OK
+	
+    In ideal cases the api should, return the updated password entity in response body.
+
+    ```json
+    {
+        "id": "int",
+        "domain": "string",
+        "username": "string",
+        "passwords": "string",
+        "notes": "string",
+        "created-at": "string",
+        "updated-at": "string",
+    }, 
+    ```
+
+- 404 NOT FOUND
+	
+    In cases where resource(password) not exist, the api should return 404.
+
+
+**Note**:
+
+...
+
+---
+
+### DELETE /passwords/:id
+
+It is used by passcodes app to delete data of a specific password entity.
+
+**Responsible**:
+
+for deleting the single password entity by its id.
+
+**Request**:
+
+will be a delete request with a `:id` as a path parameter.
+
+**Responses**:
+
+- 204 NO CONTENT
+	
+    In ideal cases the api should, return no body.
+
+- 404 NOT FOUND
+	
+    In cases where resource(password) not exist, the api should return 404.
+
+**Note**:
+
+....
+