diff --git a/openapi/components/schemas/poll.yaml b/openapi/components/schemas/poll.yaml
index e1519fc..e3f83cf 100644
--- a/openapi/components/schemas/poll.yaml
+++ b/openapi/components/schemas/poll.yaml
@@ -19,6 +19,8 @@ properties:
   grades:
     type: array
     description: The grades on which one judges a candidate.
+    minItems: 2
+    maxItems: 10
     items:
       $ref: ./grade.yaml
   judges:
diff --git a/openapi/components/schemas/result.yaml b/openapi/components/schemas/result.yaml
index 8e684d4..ad73e95 100644
--- a/openapi/components/schemas/result.yaml
+++ b/openapi/components/schemas/result.yaml
@@ -10,6 +10,8 @@ properties:
       according to the grades list, following the order of the candidates array
       defined when the related poll has been created.
     examples: [0, 6, 3, 2, 2]
+    minItems: 2
+    maxItems: 20
     items:
       type: integer
       format: int16