diff --git a/quantinuum-hugr-py/src/quantinuum_hugr/serialization/ops.py b/quantinuum-hugr-py/src/quantinuum_hugr/serialization/ops.py
index b5da17687..2bc9824dd 100644
--- a/quantinuum-hugr-py/src/quantinuum_hugr/serialization/ops.py
+++ b/quantinuum-hugr-py/src/quantinuum_hugr/serialization/ops.py
@@ -168,10 +168,6 @@ class DataflowBlock(BaseOp):
     extension_delta: ExtensionSet = Field(default_factory=list)
 
     def insert_port_types(self, in_types: TypeRow, out_types: TypeRow) -> None:
-        # The types will be all None because it's not dataflow, but we only care about
-        # the number of outputs. Note that we don't make use of the HUGR feature where
-        # the variant data is appended to successor input. Thus, `predicate_variants`
-        # will only contain empty rows.
         num_cases = len(out_types)
         self.sum_rows = [[] for _ in range(num_cases)]
 
@@ -192,7 +188,15 @@ def insert_child_dfg_signature(self, inputs: TypeRow, outputs: TypeRow) -> None:
     class Config:
         # Needed to avoid random '\n's in the pydantic description
         json_schema_extra = {
-            "description": "A CFG basic block node. The signature is that of the internal Dataflow graph."
+            "required": [
+                "parent",
+                "op",
+                "inputs",
+                "other_outputs",
+                "sum_rows",
+                "extension_delta",
+            ],
+            "description": "A CFG basic block node. The signature is that of the internal Dataflow graph.",
         }
 
 
@@ -478,9 +482,6 @@ class TypeApply(LeafOpBase):
 class TypeApplication(BaseModel):
     """Records details of an application of a PolyFuncType to some TypeArgs and the
     result (a less-, but still potentially-, polymorphic type).
-
-    Note that Guppy only generates full type applications, where the result is a
-    monomorphic type. Partial type applications are not used by Guppy.
     """
 
     input: PolyFuncType
diff --git a/quantinuum-hugr-py/src/quantinuum_hugr/serialization/tys.py b/quantinuum-hugr-py/src/quantinuum_hugr/serialization/tys.py
index ce8289ac4..effc53d18 100644
--- a/quantinuum-hugr-py/src/quantinuum_hugr/serialization/tys.py
+++ b/quantinuum-hugr-py/src/quantinuum_hugr/serialization/tys.py
@@ -161,21 +161,13 @@ class UnitSum(BaseModel):
 
 
 class GeneralSum(BaseModel):
-    """General sum type that explicitly stores the types of the variants"""
+    """General sum type that explicitly stores the types of the variants."""
 
     t: Literal["Sum"] = "Sum"
 
     s: Literal["General"] = "General"
     rows: list["TypeRow"]
 
-    class Config:
-        # Needed to avoid random '\n's in the pydantic description
-        json_schema_extra = {
-            "description": (
-                "General sum type that explicitly stores the types of the variants."
-            )
-        }
-
 
 class SumType(RootModel):
     root: Union[UnitSum, GeneralSum] = Field(discriminator="s")
diff --git a/specification/schema/hugr_schema_v1.json b/specification/schema/hugr_schema_v1.json
index 0c41b4ea0..3e0a38165 100644
--- a/specification/schema/hugr_schema_v1.json
+++ b/specification/schema/hugr_schema_v1.json
@@ -383,7 +383,12 @@
                 }
             },
             "required": [
-                "parent"
+                "parent",
+                "op",
+                "inputs",
+                "other_outputs",
+                "sum_rows",
+                "extension_delta"
             ],
             "title": "DataflowBlock",
             "type": "object"