fix: rename edit_diagram type field to operation for better model compatibility (#402)

Fixes #374 - Models were confused by the `type` field name and sent
`operation` instead. This change:

- Renames DiagramOperation.type to DiagramOperation.operation across
  all files (MCP server, web app, hooks, components, system prompts)
- Adds JSON examples in tool descriptions to show correct format
- Updates all test data to use the new field name

Affected files:
- lib/utils.ts
- app/api/chat/route.ts
- hooks/use-diagram-tool-handlers.ts
- components/chat-message-display.tsx
- lib/system-prompts.ts
- packages/mcp-server/src/diagram-operations.ts
- packages/mcp-server/src/index.ts
- scripts/test-diagram-operations.mjs

MCP server version bumped to 0.1.6

packages/mcp-server/package.json

@@ -1,6 +1,6 @@
 {
     "name": "@next-ai-drawio/mcp-server",
-    "version": "0.1.5",
+    "version": "0.1.6",
     "description": "MCP server for Next AI Draw.io - AI-powered diagram generation with real-time browser preview",
     "type": "module",
     "main": "dist/index.js",

packages/mcp-server/src/diagram-operations.ts

@@ -4,7 +4,7 @@
  */
 
 export interface DiagramOperation {
-    type: "update" | "add" | "delete"
+    operation: "update" | "add" | "delete"
     cell_id: string
     new_xml?: string
 }
@@ -77,7 +77,7 @@ export function applyDiagramOperations(
 
     // Process each operation
     for (const op of operations) {
-        if (op.type === "update") {
+        if (op.operation === "update") {
             const existingCell = cellMap.get(op.cell_id)
             if (!existingCell) {
                 errors.push({
@@ -129,7 +129,7 @@ export function applyDiagramOperations(
 
             // Update the map with the new element
             cellMap.set(op.cell_id, importedNode)
-        } else if (op.type === "add") {
+        } else if (op.operation === "add") {
             // Check if ID already exists
             if (cellMap.has(op.cell_id)) {
                 errors.push({
@@ -181,7 +181,7 @@ export function applyDiagramOperations(
 
             // Add to map
             cellMap.set(op.cell_id, importedNode)
-        } else if (op.type === "delete") {
+        } else if (op.operation === "delete") {
             const existingCell = cellMap.get(op.cell_id)
             if (!existingCell) {
                 errors.push({

packages/mcp-server/src/index.ts

@@ -265,14 +265,22 @@ server.registerTool(
             "- add: Add a new cell. Provide cell_id (new unique id) and new_xml.\n" +
             "- update: Replace an existing cell by its id. Provide cell_id and complete new_xml.\n" +
             "- delete: Remove a cell by its id. Only cell_id is needed.\n\n" +
-            "For add/update, new_xml must be a complete mxCell element including mxGeometry.",
+            "For add/update, new_xml must be a complete mxCell element including mxGeometry.\n\n" +
+            "Example - Add a rectangle:\n" +
+            '{"operations": [{"operation": "add", "cell_id": "rect-1", "new_xml": "<mxCell id=\\"rect-1\\" value=\\"Hello\\" style=\\"rounded=0;\\" vertex=\\"1\\" parent=\\"1\\"><mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/></mxCell>"}]}\n\n' +
+            "Example - Update a cell:\n" +
+            '{"operations": [{"operation": "update", "cell_id": "3", "new_xml": "<mxCell id=\\"3\\" value=\\"New Label\\" style=\\"rounded=1;\\" vertex=\\"1\\" parent=\\"1\\"><mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/></mxCell>"}]}\n\n' +
+            "Example - Delete a cell:\n" +
+            '{"operations": [{"operation": "delete", "cell_id": "rect-1"}]}',
         inputSchema: {
             operations: z
                 .array(
                     z.object({
-                        type: z
+                        operation: z
                             .enum(["update", "add", "delete"])
-                            .describe("Operation type"),
+                            .describe(
+                                "Operation to perform: add, update, or delete",
+                            ),
                         cell_id: z.string().describe("The id of the mxCell"),
                         new_xml: z
                             .string()
@@ -356,13 +364,13 @@ server.registerTool(
                     )
                     if (fixed) {
                         log.info(
-                            `Operation ${op.type} ${op.cell_id}: XML auto-fixed: ${fixes.join(", ")}`,
+                            `Operation ${op.operation} ${op.cell_id}: XML auto-fixed: ${fixes.join(", ")}`,
                         )
                         return { ...op, new_xml: fixed }
                     }
                     if (!valid && error) {
                         log.warn(
-                            `Operation ${op.type} ${op.cell_id}: XML validation failed: ${error}`,
+                            `Operation ${op.operation} ${op.cell_id}: XML validation failed: ${error}`,
                         )
                     }
                 }