diff --git a/extensions/copilot/src/extension/tools/node/editNotebookTool.tsx b/extensions/copilot/src/extension/tools/node/editNotebookTool.tsx
index 69455d8a5f0..348ddabfa3f 100644
--- a/extensions/copilot/src/extension/tools/node/editNotebookTool.tsx
+++ b/extensions/copilot/src/extension/tools/node/editNotebookTool.tsx
@@ -18,7 +18,7 @@ import { IPromptPathRepresentationService } from '../../../platform/prompts/comm
 import { ITelemetryService } from '../../../platform/telemetry/common/telemetry';
 import { IWorkspaceService } from '../../../platform/workspace/common/workspaceService';
 import { createSha256Hash } from '../../../util/common/crypto';
-import { findCell, findNotebook } from '../../../util/common/notebooks';
+import { findCell, findNotebook, isJupyterNotebook } from '../../../util/common/notebooks';
 import { findLast } from '../../../util/vs/base/common/arraysFind';
 import { raceCancellation, StatefulPromise } from '../../../util/vs/base/common/async';
 import { isCancellationError } from '../../../util/vs/base/common/errors';
@@ -317,6 +317,13 @@ export class EditNotebookTool implements ICopilotTool<IEditNotebookToolParams> {
 				if (newCode === undefined) {
 					throw new ErrorWithTelemetrySafeReason('None of the edits were applied as newCode is required for insert operation', 'missingNewCode');
 				}
+				if (newCode.length && isJupyterNotebook(notebook)) {
+					if (newCode.startsWith('{') && newCode.includes('"cell_type') && newCode.includes('"source') && newCode.endsWith('}')) {
+						// Possible the entire notebook JSON was provided as newCode.
+						// This is not supported.
+						throw new ErrorWithTelemetrySafeReason('When inserting cell(s) do NOT provide the entire notebook JSON as newCode. Provide the code (as plain text) for the cell instead.', 'gotEntireNotebookJson');
+					}
+				}
 				break;
 			case 'delete':
 				if (!id) {
diff --git a/extensions/copilot/src/util/common/notebooks.ts b/extensions/copilot/src/util/common/notebooks.ts
index d62272b566c..c06231f2738 100644
--- a/extensions/copilot/src/util/common/notebooks.ts
+++ b/extensions/copilot/src/util/common/notebooks.ts
@@ -115,6 +115,10 @@ export function isJupyterNotebookUri(uri: vscode.Uri): boolean {
 	return uri.path.endsWith('.ipynb');
 }
 
+export function isJupyterNotebook(notebook: vscode.NotebookDocument): boolean {
+	return notebook.notebookType === 'jupyter-notebook';
+}
+
 
 export function serializeNotebookDocument(document: vscode.NotebookDocument, features: { cell_uri_fragment?: boolean } = {}): string {
 	return JSON.stringify({