integration/Plugins/BlueprintMCP/Source/BlueprintMCP/Private/Handlers/UMCPHandler_SetMaterialExpressionPosition.Notes.md

UMCPHandler_SetMaterialExpressionPosition - Refactoring Notes

Changes Made

• Plain-text output: Switched from JSON Handle(FJsonObject*) to plain-text Handle(FStringBuilderBase&). Output is now concise single-line confirmation.
• FormatName/Identifies: Node lookup now uses MCPUtils::Identifies(Node, MatNode->MaterialExpression) instead of raw GUID string comparison. Output uses MCPUtils::FormatName() for the expression name. Updated the parameter description to guide callers toward using FormatName-style identifiers.
• Removed UE_LOG: Both UE_LOG calls removed. Errors and results go through the response.
• Concise output: No longer echoes the material name or command parameters back. Just reports what was moved and where. Save failure is noted inline rather than as a separate field.
• Error reporting: Uses MCPErrorCallback(Result).SetError(...) for consistency.
• Trimmed includes: Removed ~25 unnecessary includes (factory headers, JSON serialization, GUID, file helpers, blueprint editor utils, etc.). Only headers actually needed are kept.

What Looks Good

• The handler correctly updates both the graph node position and the underlying MaterialExpression editor position, which is important for keeping them in sync.
• The PreEditChange/PostEditChange bracketing is correct.
• MCPAssetFinder usage was already in good shape for loading the material/function.

Areas of Uncertainty

• MCPUtils::Identifies for UMaterialExpression: I used Identifies(Node, MatNode->MaterialExpression) based on the declaration in MCPUtils.h. I did not verify the implementation to confirm what name formats it accepts. If it only matches FormatName output (and not raw GUIDs), this is a behavioral change from the original which matched by GUID. Callers would need to use the expression name from DumpMaterial output instead of a GUID. This seems like the right direction per coding standards, but existing callers using GUIDs would break.

Possible Future Work

• Batch support: This handler moves one expression at a time. A layout operation typically repositions many nodes. A batch variant accepting an array of {node, x, y} tuples would reduce round-trips significantly.
• MCPFetcher integration: There's no MCPFetcher walker for material expressions currently. If one were added, the material/function loading and expression lookup could collapse into a single F.Walk(path) call.