diff --git a/Plugins/UEWingman/Source/UEWingman/Private/WingPropHandle.cpp b/Plugins/UEWingman/Source/UEWingman/Private/WingPropHandle.cpp
index 8c14d0a3..6d9003aa 100644
--- a/Plugins/UEWingman/Source/UEWingman/Private/WingPropHandle.cpp
+++ b/Plugins/UEWingman/Source/UEWingman/Private/WingPropHandle.cpp
@@ -274,6 +274,31 @@ WingPropHandle::Handles WingPropHandle::GetDetails(UObject* Obj, bool Mutable)
 
 	return Result;
 }
+/////////////////////////////////////////////////////////////////////////////
+//
+// Organize by Name
+//
+/////////////////////////////////////////////////////////////////////////////
+
+bool WingPropHandle::OrganizeByName(const Handles &HList, TMap<FName, TSharedPtr<IPropertyHandle>> &Result)
+{
+	Result.Empty();
+	TSet<FName> DuplicateNames;
+	for (const TSharedPtr<IPropertyHandle> &H : HList)
+	{
+		FName Name = H->GetProperty()->GetFName();
+		if (Result.Contains(Name)) DuplicateNames.Add(Name);
+		else Result.Add(Name, H);
+	}
+	if (DuplicateNames.IsEmpty()) return true;
+	UWingServer::Print(TEXT("More than one property with name:"));
+	for (FName DupName : DuplicateNames)
+	{
+		UWingServer::Printf(TEXT(" %s"), *WingUtils::ExternalizeID(DupName));
+	}
+	UWingServer::Print(TEXT("\n"));
+	return false;
+}
 
 /////////////////////////////////////////////////////////////////////////////
 //
@@ -426,6 +451,59 @@ bool WingPropHandle::SetJson(IPropertyHandle& Handle, const TSharedPtr<FJsonValu
 	return true;
 }
 
+bool WingPropHandle::PopulateFromJson(TArray<TSharedPtr<IPropertyHandle>>& Props, const FJsonObject& Json, bool AllOptional)
+{
+	bool Ok = true;
+
+	// Organize the properties by name.
+	TMap<FName, TSharedPtr<IPropertyHandle>> OrganizedProps;
+	if (!OrganizeByName(Props, OrganizedProps)) Ok = false;
+
+	// Parse the keys in the json, make sure they're syntactically valid and
+	// that they match the names of actual properties, and that there are no dups.
+	TSet<FName> Specified;
+	for (const auto& KV : Json.Values)
+	{
+		FName Name = WingUtils::CheckInternalizeID(KV.Key);
+		if (Name.IsNone()) { Ok = false; continue; }
+		if (!OrganizedProps.Contains(Name))
+		{
+			UWingServer::Printf(TEXT("ERROR: Unknown parameter '%s'\n"), *KV.Key);
+			Ok = false;
+		}
+		if (!WingUtils::FindNoDuplicateName(Specified, Name, TEXT("parameter"))) Ok = false;
+	}
+
+	// Make sure that all required properties have been specified.
+	if (!AllOptional)
+	{
+		for (const TSharedPtr<IPropertyHandle> &H : Props)
+		{
+			if (H->HasMetaData(TEXT("Optional"))) continue;
+			FName Name = H->GetProperty()->GetFName();
+			if (!Specified.Contains(Name))
+			{
+				UWingServer::Printf(TEXT("Required parameter %s not specified\n"),
+					*WingUtils::ExternalizeID(Name));
+				Ok = false;
+			}
+		}
+	}
+
+	// If anything is wrong, return early without setting anything.
+	if (!Ok) return false;
+
+	// Populate each property from JSON.  This could fail too, but at this
+	// point, we're committed.
+	for (const auto& KV : Json.Values)
+	{
+		FName Name = WingUtils::CheckInternalizeID(KV.Key);
+		if (!SetJson(*OrganizedProps[Name], KV.Value)) Ok = false;
+	}
+	return Ok;
+}
+
+
 /////////////////////////////////////////////////////////////////////////////
 //
 // Print
diff --git a/Plugins/UEWingman/Source/UEWingman/Private/WingServer.cpp b/Plugins/UEWingman/Source/UEWingman/Private/WingServer.cpp
index c440720a..9a66395c 100644
--- a/Plugins/UEWingman/Source/UEWingman/Private/WingServer.cpp
+++ b/Plugins/UEWingman/Source/UEWingman/Private/WingServer.cpp
@@ -1,6 +1,6 @@
 #include "WingServer.h"
 #include "WingHandler.h"
-#include "WingProperty.h"
+#include "WingPropHandle.h"
 #include "WingManual.h"
 #include "WingLogCapture.h"
 #include "WingUtils.h"
@@ -328,7 +328,9 @@ void UWingServer::TryCallHandler(const FString &Line)
 	Handler->ConfigurationObject = Found->Config.Get();
 
 	// Populate the handler object with the request parameters.
-	if (!FWingProperty::PopulateFromJson(HandlerObj->GetClass(), HandlerObj.Get(), &*Request))
+	WingPropHandle Props;
+	WingPropHandle::Handles Handles = Props.AllProperties(HandlerObj.Get(), true, CPF_None);
+	if (!WingPropHandle::PopulateFromJson(Handles, *Request, false))
 	{
 		UWingServer::SuggestManual(WingManual::Section::HandlerHelp);
 		return;
diff --git a/Plugins/UEWingman/Source/UEWingman/Private/WingUtils.cpp b/Plugins/UEWingman/Source/UEWingman/Private/WingUtils.cpp
index dafc76ad..da36a9e4 100644
--- a/Plugins/UEWingman/Source/UEWingman/Private/WingUtils.cpp
+++ b/Plugins/UEWingman/Source/UEWingman/Private/WingUtils.cpp
@@ -56,9 +56,6 @@
 // Name sanitization
 // ============================================================
 
-FName WingUtils::GetFName(const FWingProperty &Prop) { return Prop.Prop->GetFName(); }
-FName WingUtils::GetFName(const TSharedPtr<IPropertyHandle> &H) { return H->GetProperty()->GetFName(); }
-
 FString WingUtils::ExternalizeID(FName Name)
 {
 	return WingTokenizer::ExternalizeID(Name);
@@ -272,6 +269,17 @@ FString WingUtils::FormatName(const UWidget *Widget)
 	return ExternalizeID(Widget->GetFName());
 }
 
+FName WingUtils::GetFName(const FWingProperty &Prop)
+{
+	return Prop.Prop->GetFName();
+}
+
+FName WingUtils::GetFName(const TSharedPtr<IPropertyHandle> &H)
+{
+	return H->GetProperty()->GetFName();
+}
+
+
 // ============================================================
 // Formatting other things
 // ============================================================
diff --git a/Plugins/UEWingman/Source/UEWingman/Public/WingPropHandle.h b/Plugins/UEWingman/Source/UEWingman/Public/WingPropHandle.h
index 8809b7d2..77011a8a 100644
--- a/Plugins/UEWingman/Source/UEWingman/Public/WingPropHandle.h
+++ b/Plugins/UEWingman/Source/UEWingman/Public/WingPropHandle.h
@@ -4,6 +4,9 @@
 #include "IPropertyRowGenerator.h"
 #include "PropertyHandle.h"
 
+class FJsonObject;
+class FJsonValue;
+
 // WingPropHandle: A module that provides easy access to
 // IPropertyHandle objects.  To use this module, construct a
 // WingPropHandle, then use it to fetch properties from
@@ -52,13 +55,27 @@ public:
 	// expression properties), widgets (includes slot properties).
 	Handles GetDetails(UObject* Obj, bool Mutable);
 
-	// Get/set text with special handling for enums (smarter prefix
-	// matching via WingUtils::StringToEnum) and FEdGraphPinType
-	// (human-readable format via UWingTypes).
+	// Organize properties by name.  If there's more than one property
+	// of a given name, print an error and returns false, and returns a map
+	// that contains one of the two duplicates.
+	static bool OrganizeByName(const Handles &H, TMap<FName, TSharedPtr<IPropertyHandle>> &Result);
+
+	// Get/set text.  Compared to the built in methods for getting and setting
+	// text, these support more concise enum values, FEdGraphPinType, and
+	// more concise Class properties.
 	static FString GetText(IPropertyHandle& Handle);
 	static bool SetText(IPropertyHandle& Handle, const FString& Text);
+
+	// Store a Json value into a property handle.  The Json value must be
+	// a string, number, or boolean.
 	static bool SetJson(IPropertyHandle& Handle, const TSharedPtr<FJsonValue>& JsonValue);
 
+	// Populate a whole bunch of properties from a Json object.  If
+	// AllOptional is true, the Json may supply a subset of the properties.
+	// If not, the Json must supply all of them, excepting properties that
+	// are explicitly marked Optional.
+	static bool PopulateFromJson(TArray<TSharedPtr<IPropertyHandle>>& Props, const FJsonObject& Json, bool AllOptional);
+	
 	// Print a single property in a standardized format:
 	//     editable|readonly Type Name = Value
 	static void Print(IPropertyHandle& Handle, FStringBuilderBase& Out);