diff --git a/hiku/validate/graph.py b/hiku/validate/graph.py
index 70b35ef..b816201 100644
--- a/hiku/validate/graph.py
+++ b/hiku/validate/graph.py
@@ -20,11 +20,16 @@
 )
 from ..graph import AbstractNode, AbstractField, AbstractLink, AbstractOption
 
+from ..compat import Protocol
 from .errors import Errors
 from ..scalar import Scalar
 from ..types import GenericMeta, OptionalMeta
 
 
+class DescriptionProtocol(Protocol):
+    description: t.Optional[str]
+
+
 class GraphValidationError(TypeError):
     def __init__(self, errors: t.List[str]) -> None:
         self.errors = errors
@@ -134,6 +139,15 @@ def _validate_deprecated_duplicates(
                 )
             )
 
+    def _validate_description(self, obj: DescriptionProtocol) -> None:
+        if obj.description is not None:
+            if not isinstance(obj.description, str):
+                self.errors.report(
+                    '{} "{}" description must be a string'.format(
+                        obj.__class__.__name__, self._format_path(obj)
+                    ),
+                )
+
     def visit_option(self, obj: Option) -> None:
         if (
             isinstance(obj.type, GenericMeta)
@@ -146,6 +160,8 @@ def visit_option(self, obj: Option) -> None:
                 ),
             )
 
+        self._validate_description(obj)
+
     def visit_field(self, obj: Field) -> None:
         invalid = [
             f
@@ -186,6 +202,7 @@ def visit_field(self, obj: Field) -> None:
             )
             return
 
+        self._validate_description(obj)
         self._validate_deprecated_duplicates(obj)
 
     def visit_link(self, obj: Link) -> None:
@@ -230,6 +247,7 @@ def visit_link(self, obj: Link) -> None:
                         )
                     )
 
+        self._validate_description(obj)
         self._validate_deprecated_duplicates(obj)
 
     def visit_node(self, obj: Node) -> None:
@@ -269,6 +287,8 @@ def visit_node(self, obj: Node) -> None:
                         )
                     )
 
+        self._validate_description(obj)
+
     def visit_union(self, obj: "Union") -> t.Any:
         if not obj.name:
             self.errors.report("Union must have a name")
@@ -288,6 +308,8 @@ def visit_union(self, obj: "Union") -> t.Any:
             )
             return
 
+        self._validate_description(obj)
+
     def visit_interface(self, obj: "Interface") -> t.Any:
         if not obj.name:
             self.errors.report("Interface must have a name")
@@ -311,6 +333,8 @@ def visit_interface(self, obj: "Interface") -> t.Any:
             )
             return
 
+        self._validate_description(obj)
+
     def visit_enum(self, obj: BaseEnum) -> t.Any:
         if not obj.name:
             self.errors.report("Enum must have a name")
@@ -320,6 +344,8 @@ def visit_enum(self, obj: BaseEnum) -> t.Any:
             self.errors.report("Enum must have at least one value")
             return
 
+        self._validate_description(obj)
+
     def visit_scalar(self, obj: t.Type[Scalar]) -> t.Any:
         ...
 
diff --git a/tests/test_validate_graph.py b/tests/test_validate_graph.py
index e33a178..8b6cf8b 100644
--- a/tests/test_validate_graph.py
+++ b/tests/test_validate_graph.py
@@ -283,3 +283,12 @@ def test_link_uses_more_than_one_deprecated_directive():
         ],
         ['Deprecated directive must be used only once for "bar.baz", found 2'],
     )
+
+
+def test_graph_contain_duplicate_nodes():
+    check_errors(
+        [
+            Node("foo", [], description=tuple("foo")),
+        ],
+        ['Node "foo" description must be a string'],
+    )
\ No newline at end of file