mcp: formally adopt 2025-06-18 spec (microsoft#252004)

Still todo:
- Support structured output
- Add resource_link support to tool results

Also add an event for elicitation

Ref microsoft#248418

Author: connor4312

src/vs/workbench/contrib/mcp/browser/mcpPromptArgumentPick.ts

@@ -76,7 +76,7 @@ export class McpPromptArgumentPick extends Disposable {
 			const restore = backSnapshots.at(i);
 			quickPick.step = i + 1;
 			quickPick.placeholder = arg.required ? arg.description : `${arg.description || ''} (${localize('optional', 'Optional')})`;
-			quickPick.title = localize('mcp.prompt.pick.title', 'Value for: {0}', arg.name);
+			quickPick.title = localize('mcp.prompt.pick.title', 'Value for: {0}', arg.title || arg.name);
 			quickPick.value = restore?.value ?? ((args.hasOwnProperty(arg.name) && args[arg.name]) || '');
 			quickPick.items = restore?.items ?? [];
 			quickPick.activeItems = restore?.activeItems ?? [];

src/vs/workbench/contrib/mcp/browser/mcpResourceQuickAccess.ts

@@ -40,15 +40,15 @@ export class McpResourcePickHelper {
 		if (isMcpResourceTemplate(resource)) {
 			return {
 				id: resource.template.template,
-				label: resource.name,
+				label: resource.title || resource.name,
 				description: resource.description,
 				detail: localize('mcp.resource.template', 'Resource template: {0}', resource.template.template),
 			};
 		}
 
 		return {
 			id: resource.uri.toString(),
-			label: resource.name,
+			label: resource.title || resource.name,
 			description: resource.description,
 			detail: resource.mcpUri + (resource.sizeInBytes !== undefined ? ' (' + ByteSize.formatSize(resource.sizeInBytes) + ')' : ''),
 		};

src/vs/workbench/contrib/mcp/common/mcpServer.ts

@@ -55,6 +55,18 @@ type ServerBootClassification = {
 	serverVersion: { classification: 'SystemMetaData'; purpose: 'FeatureInsight'; comment: 'The version of the MCP server' };
 };
 
+type ElicitationTelemetryData = {
+	serverName: string;
+	serverVersion: string;
+};
+
+type ElicitationTelemetryClassification = {
+	owner: 'connor4312';
+	comment: 'Triggered when elictation is requested';
+	serverName: { classification: 'SystemMetaData'; purpose: 'FeatureInsight'; comment: 'The name of the MCP server' };
+	serverVersion: { classification: 'SystemMetaData'; purpose: 'FeatureInsight'; comment: 'The version of the MCP server' };
+};
+
 type ServerBootState = {
 	state: string;
 	time: number;
@@ -477,8 +489,17 @@ export class McpServer extends Disposable implements IMcpServer {
 					server: this,
 					params,
 				}).then(r => r.sample),
-				elicitationRequestHandler: req => this._elicitationService.elicit(
-					this, Iterable.first(this.runningToolCalls), req, CancellationToken.None),
+				elicitationRequestHandler: req => {
+					const serverInfo = connection.handler.get()?.serverInfo;
+					if (serverInfo) {
+						this._telemetryService.publicLog2<ElicitationTelemetryData, ElicitationTelemetryClassification>('mcp.elicitationRequested', {
+							serverName: serverInfo.name,
+							serverVersion: serverInfo.version,
+						});
+					}
+
+					return this._elicitationService.elicit(this, Iterable.first(this.runningToolCalls), req, CancellationToken.None);
+				}
 			});
 
 			this._telemetryService.publicLog2<ServerBootState, ServerBootStateClassification>('mcp/serverBootState', {
@@ -670,6 +691,7 @@ class McpPrompt implements IMcpPrompt {
 	readonly id: string;
 	readonly name: string;
 	readonly description?: string;
+	readonly title?: string;
 	readonly arguments: readonly MCP.PromptArgument[];
 
 	constructor(
@@ -678,6 +700,7 @@ class McpPrompt implements IMcpPrompt {
 	) {
 		this.id = mcpPromptReplaceSpecialChars(this._server.definition.label + '.' + _definition.name);
 		this.name = _definition.name;
+		this.title = _definition.title;
 		this.description = _definition.description;
 		this.arguments = _definition.arguments || [];
 	}
@@ -824,18 +847,20 @@ function warnInvalidTools(instaService: IInstantiationService, serverName: strin
 }
 
 class McpResource implements IMcpResource {
-	uri: URI;
-	mcpUri: string;
-	name: string;
-	description: string | undefined;
-	mimeType: string | undefined;
-	sizeInBytes: number | undefined;
+	readonly uri: URI;
+	readonly mcpUri: string;
+	readonly name: string;
+	readonly description: string | undefined;
+	readonly mimeType: string | undefined;
+	readonly sizeInBytes: number | undefined;
+	readonly title: string | undefined;
 
 	constructor(
 		server: McpServer,
 		original: MCP.Resource,
 	) {
 		this.mcpUri = original.uri;
+		this.title = original.title;
 		this.uri = McpResourceURI.fromServer(server.definition, original.uri);
 		this.name = original.name;
 		this.description = original.description;
@@ -846,6 +871,7 @@ class McpResource implements IMcpResource {
 
 class McpResourceTemplate implements IMcpResourceTemplate {
 	readonly name: string;
+	readonly title?: string | undefined;
 	readonly description?: string;
 	readonly mimeType?: string;
 	readonly template: UriTemplate;
@@ -857,6 +883,7 @@ class McpResourceTemplate implements IMcpResourceTemplate {
 		this.name = _definition.name;
 		this.description = _definition.description;
 		this.mimeType = _definition.mimeType;
+		this.title = _definition.title;
 		this.template = UriTemplate.parse(_definition.uriTemplate);
 	}
 

src/vs/workbench/contrib/mcp/common/mcpService.ts

@@ -114,7 +114,8 @@ export class McpService extends Disposable implements IMcpService {
 					id: tool.id,
 					source,
 					icon: Codicon.tools,
-					displayName: tool.definition.annotations?.title || tool.definition.name,
+					// duplicative: https://github.com/modelcontextprotocol/modelcontextprotocol/pull/813
+					displayName: tool.definition.annotations?.title || tool.definition.title || tool.definition.name,
 					toolReferenceName: tool.referenceName,
 					modelDescription: tool.definition.description ?? '',
 					userDescription: tool.definition.description ?? '',
@@ -256,7 +257,8 @@ class McpToolImplementation implements IToolImpl {
 		);
 
 		const needsConfirmation = !tool.definition.annotations?.readOnlyHint;
-		const title = tool.definition.annotations?.title || ('`' + tool.definition.name + '`');
+		// duplicative: https://github.com/modelcontextprotocol/modelcontextprotocol/pull/813
+		const title = tool.definition.annotations?.title || tool.definition.title || ('`' + tool.definition.name + '`');
 		const subtitle = localize('msg.subtitle', "{0} (MCP Server)", server.definition.label);
 
 		return {
@@ -324,6 +326,8 @@ class McpToolImplementation implements IToolImpl {
 			} else if (item.type === 'image' || item.type === 'audio') {
 				// default to some image type if not given to hint
 				addAsInlineData(item.mimeType || 'image/png', item.data);
+			} else if (item.type === 'resource_link') {
+				// todo@connor4312 look at what we did before #250329 and use that here
 			} else if (item.type === 'resource') {
 				const uri = McpResourceURI.fromServer(this._server.definition, item.resource.uri);
 				if (item.resource.mimeType && getAttachableImageExtension(item.resource.mimeType) && 'blob' in item.resource) {

src/vs/workbench/contrib/mcp/common/mcpTypes.ts

@@ -283,13 +283,15 @@ export interface IMcpResource {
 	/** Identifier of the file as given from the MCP server. */
 	readonly mcpUri: string;
 	readonly name: string;
+	readonly title?: string;
 	readonly description?: string;
 	readonly mimeType?: string;
 	readonly sizeInBytes?: number;
 }
 
 export interface IMcpResourceTemplate {
 	readonly name: string;
+	readonly title?: string;
 	readonly description?: string;
 	readonly mimeType?: string;
 	readonly template: UriTemplate;
@@ -326,6 +328,7 @@ export const enum McpServerCacheState {
 export interface IMcpPrompt {
 	readonly id: string;
 	readonly name: string;
+	readonly title?: string;
 	readonly description?: string;
 	readonly arguments: readonly MCP.PromptArgument[];