diff --git a/cmd/api-server/main.go b/cmd/api-server/main.go
index 72d652f..a0be3fd 100644
--- a/cmd/api-server/main.go
+++ b/cmd/api-server/main.go
@@ -13,14 +13,14 @@ type Transaction struct {
 	Date        string  `json:"date"`
 	Description string  `json:"description"`
 	Value       float64 `json:"value"`
-	Category    string  `json:"category"`
+	Category    string  `json:"category,omitempty"`
 }
 
 // Bank struct represents a bank
 type Bank struct {
 	ID         string `json:"id"`
 	Name       string `json:"name"`
-	NordigenID string `json:"nordigenId"`
+	NordigenID string `json:"nordigenId,omitempty"`
 }
 
 // ResponseError struct represents an error response
diff --git a/docs/openapi.yaml b/docs/openapi.yaml
index 16f1c6b..ead13b4 100644
--- a/docs/openapi.yaml
+++ b/docs/openapi.yaml
@@ -132,6 +132,11 @@ components:
           format: float
         category:
           type: string
+      required:
+        - id
+        - date
+        - description
+        - value
     Transactions:
       type: array
       items:
@@ -146,6 +151,9 @@ components:
         nordigenId:
           type: string
           format: uuid
+      required:
+        - id
+        - name
     Banks:
       type: array
       items: