diff --git a/datamodel/low/model_interfaces.go b/datamodel/low/model_interfaces.go
index d5054ee..782acb6 100644
--- a/datamodel/low/model_interfaces.go
+++ b/datamodel/low/model_interfaces.go
@@ -5,15 +5,24 @@ package low
 
 type SharedParameters interface {
 	Hash() [32]byte
-	GetType() *NodeReference[string]
+	GetName() *NodeReference[string]
+	GetIn() *NodeReference[string]
 	GetDescription() *NodeReference[string]
-	GetDeprecated() *NodeReference[bool]
+	GetAllowEmptyValue() *NodeReference[bool]
+	GetRequired() *NodeReference[bool]
+	GetSchema() *NodeReference[any] // requires cast.
+}
+
+type HasDescription interface {
+	GetDescription() *NodeReference[string]
+}
+
+type SwaggerParameter interface {
+	SharedParameters
+	GetType() *NodeReference[string]
 	GetFormat() *NodeReference[string]
-	GetStyle() *NodeReference[string]
 	GetCollectionFormat() *NodeReference[string]
 	GetDefault() *NodeReference[any]
-	GetAllowReserved() *NodeReference[bool]
-	GetExplode() *NodeReference[bool]
 	GetMaximum() *NodeReference[int]
 	GetExclusiveMaximum() *NodeReference[bool]
 	GetMinimum() *NodeReference[int]
@@ -26,27 +35,6 @@ type SharedParameters interface {
 	GetUniqueItems() *NodeReference[bool]
 	GetEnum() *NodeReference[[]ValueReference[string]]
 	GetMultipleOf() *NodeReference[int]
-	GetExample() *NodeReference[any]
-	GetSchema() *NodeReference[any]   // requires cast.
-	GetExamples() *NodeReference[any] // requires cast
-	GetContent() *NodeReference[any]  // requires cast.
-	GetItems() *NodeReference[any]    // requires cast.
-}
-
-type IsParameter interface {
-	GetName() *NodeReference[string]
-	GetIn() *NodeReference[string]
-	SharedParameterHeader
-	SharedParameters
-}
-
-type SharedParameterHeader interface {
-	GetRequired() *NodeReference[bool]
-	GetAllowEmptyValue() *NodeReference[bool]
-}
-
-type HasDescription interface {
-	GetDescription() *NodeReference[string]
 }
 
 type SwaggerHeader interface {
@@ -82,7 +70,18 @@ type OpenAPIHeader interface {
 	GetRequired() *NodeReference[bool]
 	GetAllowEmptyValue() *NodeReference[bool]
 	GetSchema() *NodeReference[any]   // requires cast.
-	GetExamples() *NodeReference[any] // requires cast
+	GetExamples() *NodeReference[any] // requires cast.
+	GetContent() *NodeReference[any]  // requires cast.
+}
+
+type OpenAPIParameter interface {
+	SharedParameters
+	GetDeprecated() *NodeReference[bool]
+	GetStyle() *NodeReference[string]
+	GetAllowReserved() *NodeReference[bool]
+	GetExplode() *NodeReference[bool]
+	GetExample() *NodeReference[any]
+	GetExamples() *NodeReference[any] // requires cast.
 	GetContent() *NodeReference[any]  // requires cast.
 }
 
@@ -92,10 +91,10 @@ type SharedOperations interface {
 	GetDescription() NodeReference[string]
 	GetDeprecated() NodeReference[bool]
 	GetExtensions() map[KeyReference[string]]ValueReference[any]
-	GetExternalDocs() NodeReference[any] // requires cast
-	GetResponses() NodeReference[any]    // requires cast
-	GetParameters() NodeReference[any]   // requires cast
-	GetSecurity() NodeReference[any]     // requires cast
+	GetExternalDocs() NodeReference[any] // requires cast.
+	GetResponses() NodeReference[any]    // requires cast.
+	GetParameters() NodeReference[any]   // requires cast.
+	GetSecurity() NodeReference[any]     // requires cast.
 }
 
 type SwaggerOperations interface {
@@ -108,5 +107,5 @@ type SwaggerOperations interface {
 type OpenAPIOperations interface {
 	SharedOperations
 	//GetCallbacks() NodeReference[map[KeyReference[string]]ValueReference[any]] // requires cast
-	GetServers() NodeReference[any] // requires cast
+	GetServers() NodeReference[any] // requires cast.
 }
diff --git a/datamodel/low/v2/items.go b/datamodel/low/v2/items.go
index d96371b..1778785 100644
--- a/datamodel/low/v2/items.go
+++ b/datamodel/low/v2/items.go
@@ -150,6 +150,9 @@ func (i *Items) GetItems() *low.NodeReference[any] {
 func (i *Items) GetCollectionFormat() *low.NodeReference[string] {
 	return &i.CollectionFormat
 }
+func (i *Items) GetDescription() *low.NodeReference[string] {
+	return nil // not implemented, but required to align with header contract
+}
 func (i *Items) GetDefault() *low.NodeReference[any] {
 	return &i.Default
 }
diff --git a/what-changed/model/parameter.go b/what-changed/model/parameter.go
index a0ff12f..8f17df3 100644
--- a/what-changed/model/parameter.go
+++ b/what-changed/model/parameter.go
@@ -74,7 +74,7 @@ func addPropertyCheck(props *[]*PropertyCheck,
 	})
 }
 
-func addOpenAPIParameterProperties(left, right low.IsParameter, changes *[]*Change) []*PropertyCheck {
+func addOpenAPIParameterProperties(left, right low.OpenAPIParameter, changes *[]*Change) []*PropertyCheck {
 	var props []*PropertyCheck
 
 	// style
@@ -100,7 +100,7 @@ func addOpenAPIParameterProperties(left, right low.IsParameter, changes *[]*Chan
 	return props
 }
 
-func addSwaggerParameterProperties(left, right low.IsParameter, changes *[]*Change) []*PropertyCheck {
+func addSwaggerParameterProperties(left, right low.SwaggerParameter, changes *[]*Change) []*PropertyCheck {
 	var props []*PropertyCheck
 
 	// type
@@ -166,7 +166,7 @@ func addSwaggerParameterProperties(left, right low.IsParameter, changes *[]*Chan
 	return props
 }
 
-func addCommonParameterProperties(left, right low.IsParameter, changes *[]*Change) []*PropertyCheck {
+func addCommonParameterProperties(left, right low.SharedParameters, changes *[]*Change) []*PropertyCheck {
 	var props []*PropertyCheck
 
 	addPropertyCheck(&props, left.GetName().ValueNode, right.GetName().ValueNode,
diff --git a/what-changed/model/path_item.go b/what-changed/model/path_item.go
index 9b70426..94edf3f 100644
--- a/what-changed/model/path_item.go
+++ b/what-changed/model/path_item.go
@@ -324,18 +324,18 @@ func compareSwaggerPathItem(lPath, rPath *v2.PathItem, changes *[]*Change, pc *P
 	return props
 }
 
-func extractV2ParametersIntoInterface(l, r []low.ValueReference[*v2.Parameter]) ([]low.ValueReference[low.IsParameter],
-	[]low.ValueReference[low.IsParameter]) {
-	lp := make([]low.ValueReference[low.IsParameter], len(l))
-	rp := make([]low.ValueReference[low.IsParameter], len(r))
+func extractV2ParametersIntoInterface(l, r []low.ValueReference[*v2.Parameter]) ([]low.ValueReference[low.SharedParameters],
+	[]low.ValueReference[low.SharedParameters]) {
+	lp := make([]low.ValueReference[low.SharedParameters], len(l))
+	rp := make([]low.ValueReference[low.SharedParameters], len(r))
 	for i := range l {
-		lp[i] = low.ValueReference[low.IsParameter]{
+		lp[i] = low.ValueReference[low.SharedParameters]{
 			Value:     l[i].Value,
 			ValueNode: l[i].ValueNode,
 		}
 	}
 	for i := range r {
-		rp[i] = low.ValueReference[low.IsParameter]{
+		rp[i] = low.ValueReference[low.SharedParameters]{
 			Value:     r[i].Value,
 			ValueNode: r[i].ValueNode,
 		}
@@ -343,18 +343,18 @@ func extractV2ParametersIntoInterface(l, r []low.ValueReference[*v2.Parameter])
 	return lp, rp
 }
 
-func extractV3ParametersIntoInterface(l, r []low.ValueReference[*v3.Parameter]) ([]low.ValueReference[low.IsParameter],
-	[]low.ValueReference[low.IsParameter]) {
-	lp := make([]low.ValueReference[low.IsParameter], len(l))
-	rp := make([]low.ValueReference[low.IsParameter], len(r))
+func extractV3ParametersIntoInterface(l, r []low.ValueReference[*v3.Parameter]) ([]low.ValueReference[low.SharedParameters],
+	[]low.ValueReference[low.SharedParameters]) {
+	lp := make([]low.ValueReference[low.SharedParameters], len(l))
+	rp := make([]low.ValueReference[low.SharedParameters], len(r))
 	for i := range l {
-		lp[i] = low.ValueReference[low.IsParameter]{
+		lp[i] = low.ValueReference[low.SharedParameters]{
 			Value:     l[i].Value,
 			ValueNode: l[i].ValueNode,
 		}
 	}
 	for i := range r {
-		rp[i] = low.ValueReference[low.IsParameter]{
+		rp[i] = low.ValueReference[low.SharedParameters]{
 			Value:     r[i].Value,
 			ValueNode: r[i].ValueNode,
 		}
@@ -362,10 +362,10 @@ func extractV3ParametersIntoInterface(l, r []low.ValueReference[*v3.Parameter])
 	return lp, rp
 }
 
-func checkParameters(lParams, rParams []low.ValueReference[low.IsParameter], changes *[]*Change, pc *PathItemChanges) {
+func checkParameters(lParams, rParams []low.ValueReference[low.SharedParameters], changes *[]*Change, pc *PathItemChanges) {
 
-	lv := make(map[string]low.IsParameter, len(lParams))
-	rv := make(map[string]low.IsParameter, len(rParams))
+	lv := make(map[string]low.SharedParameters, len(lParams))
+	rv := make(map[string]low.SharedParameters, len(rParams))
 
 	for i := range lParams {
 		s := lParams[i].Value.GetName().Value