diff --git a/src/vs/workbench/api/common/extHost.api.impl.ts b/src/vs/workbench/api/common/extHost.api.impl.ts
index c09e72566e7..b119a46852e 100644
--- a/src/vs/workbench/api/common/extHost.api.impl.ts
+++ b/src/vs/workbench/api/common/extHost.api.impl.ts
@@ -1972,6 +1972,7 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			McpStdioServerDefinition: extHostTypes.McpStdioServerDefinition,
 			McpStdioServerDefinition2: extHostTypes.McpStdioServerDefinition,
 			McpToolAvailability: extHostTypes.McpToolAvailability,
+			McpToolInvocationContentData: extHostTypes.McpToolInvocationContentData,
 			SettingsSearchResultKind: extHostTypes.SettingsSearchResultKind,
 		};
 	};
diff --git a/src/vs/workbench/api/common/extHostTypeConverters.ts b/src/vs/workbench/api/common/extHostTypeConverters.ts
index 10f15a6c485..b09ba368f8f 100644
--- a/src/vs/workbench/api/common/extHostTypeConverters.ts
+++ b/src/vs/workbench/api/common/extHostTypeConverters.ts
@@ -2815,6 +2815,19 @@ export namespace ChatResponseMovePart {
 
 export namespace ChatToolInvocationPart {
 	export function from(part: vscode.ChatToolInvocationPart): IChatToolInvocationSerialized {
+		// Check if toolSpecificData is ChatMcpToolInvocationData (has input and output)
+		// If so, convert to resultDetails for rendering via ChatInputOutputMarkdownProgressPart
+		let resultDetails: IToolResultInputOutputDetails | undefined;
+		let toolSpecificData: any;
+
+		if (part.toolSpecificData && isChatMcpToolInvocationData(part.toolSpecificData)) {
+			// Convert ChatMcpToolInvocationData to IToolResultInputOutputDetails
+			resultDetails = convertMcpToResultDetails(part.toolSpecificData, part.isError);
+			toolSpecificData = undefined; // MCP data goes to resultDetails, not toolSpecificData
+		} else {
+			toolSpecificData = part.toolSpecificData ? convertToolSpecificData(part.toolSpecificData) : undefined;
+		}
+
 		// Convert extension API ChatToolInvocationPart to internal serialized format
 		return {
 			kind: 'toolInvocationSerialized',
@@ -2827,7 +2840,8 @@ export namespace ChatToolInvocationPart {
 			isComplete: part.isComplete ?? true,
 			source: ToolDataSource.External,
 			// isError: part.isError ?? false,
-			toolSpecificData: part.toolSpecificData ? convertToolSpecificData(part.toolSpecificData) : undefined,
+			toolSpecificData,
+			resultDetails,
 			presentation: part.presentation === 'hidden'
 				? ToolInvocationPresentation.Hidden
 				: part.presentation === 'hiddenAfterComplete'
@@ -2837,6 +2851,28 @@ export namespace ChatToolInvocationPart {
 		};
 	}
 
+	function isChatMcpToolInvocationData(data: any): data is vscode.ChatMcpToolInvocationData {
+		return data !== null && typeof data === 'object' &&
+			'input' in data && typeof data.input === 'string' &&
+			'output' in data && Array.isArray(data.output);
+	}
+
+	function convertMcpToResultDetails(data: vscode.ChatMcpToolInvocationData, isError?: boolean): IToolResultInputOutputDetails {
+		return {
+			input: data.input,
+			output: data.output.map((o) => {
+				const isText = o.mimeType.startsWith('text/');
+				return {
+					type: 'embed' as const,
+					mimeType: o.mimeType,
+					value: isText ? VSBuffer.wrap(o.data).toString() : encodeBase64(VSBuffer.wrap(o.data)),
+					isText: isText,
+				};
+			}),
+			isError: isError ?? false,
+		};
+	}
+
 	function convertToolSpecificData(data: any): any {
 		// Convert extension API terminal tool data to internal format
 		if ('command' in data && 'language' in data) {
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index c142462a992..86ea71b91c8 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -3166,6 +3166,15 @@ export class ChatResponseMultiDiffPart {
 	}
 }
 
+export class McpToolInvocationContentData {
+	mimeType: string;
+	data: Uint8Array;
+	constructor(data: Uint8Array, mimeType: string) {
+		this.data = data;
+		this.mimeType = mimeType;
+	}
+}
+
 export class ChatResponseExternalEditPart {
 	applied: Thenable<string>;
 	didGetApplied!: (value: string) => void;
diff --git a/src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts b/src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts
index 89da67be3e1..25457624e2c 100644
--- a/src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts
+++ b/src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts
@@ -120,6 +120,30 @@ declare module 'vscode' {
 		language: string;
 	}
 
+	export class McpToolInvocationContentData {
+		/**
+		 * The mime type which determines how the data property is interpreted.
+		 */
+		mimeType: string;
+
+		/**
+		 * The byte data for this part.
+		 */
+		data: Uint8Array;
+
+		/**
+		 * Construct a generic data part with the given content.
+		 * @param data The byte data for this part.
+		 * @param mimeType The mime type of the data.
+		 */
+		constructor(data: Uint8Array, mimeType: string);
+	}
+
+	export interface ChatMcpToolInvocationData {
+		input: string;
+		output: McpToolInvocationContentData[];
+	}
+
 	export class ChatToolInvocationPart {
 		toolName: string;
 		toolCallId: string;
@@ -129,7 +153,7 @@ declare module 'vscode' {
 		pastTenseMessage?: string | MarkdownString;
 		isConfirmed?: boolean;
 		isComplete?: boolean;
-		toolSpecificData?: ChatTerminalToolInvocationData;
+		toolSpecificData?: ChatTerminalToolInvocationData | ChatMcpToolInvocationData;
 		subAgentInvocationId?: string;
 		presentation?: 'hidden' | 'hiddenAfterComplete' | undefined;