diff --git a/extensions/vscode-api-tests/src/singlefolder-tests/chat.test.ts b/extensions/vscode-api-tests/src/singlefolder-tests/chat.test.ts
index 44fa4396796..6fb0262e132 100644
--- a/extensions/vscode-api-tests/src/singlefolder-tests/chat.test.ts
+++ b/extensions/vscode-api-tests/src/singlefolder-tests/chat.test.ts
@@ -67,7 +67,7 @@ suite('chat', () => {
 				interactive.sendInteractiveRequestToProvider('provider', { message: '@participant /hello friend' });
 			} else {
 				assert.strictEqual(request.context.history.length, 1);
-				assert.strictEqual(request.context.history[0].participant.participant, 'participant');
+				assert.strictEqual(request.context.history[0].participant.name, 'participant');
 				assert.strictEqual(request.context.history[0].command, 'hello');
 			}
 		});
diff --git a/src/vs/workbench/api/common/extHostChatAgents2.ts b/src/vs/workbench/api/common/extHostChatAgents2.ts
index ad00314cac6..9f9266babba 100644
--- a/src/vs/workbench/api/common/extHostChatAgents2.ts
+++ b/src/vs/workbench/api/common/extHostChatAgents2.ts
@@ -231,11 +231,11 @@ export class ExtHostChatAgents2 implements ExtHostChatAgentsShape2 {
 				{ ...ehResult, metadata: undefined };
 
 			// REQUEST turn
-			res.push(new extHostTypes.ChatRequestTurn(h.request.message, h.request.command, h.request.variables.variables.map(typeConvert.ChatAgentResolvedVariable.to), { extensionId: '', participant: h.request.agentId }));
+			res.push(new extHostTypes.ChatRequestTurn(h.request.message, h.request.command, h.request.variables.variables.map(typeConvert.ChatAgentResolvedVariable.to), { extensionId: '', name: h.request.agentId }));
 
 			// RESPONSE turn
 			const parts = coalesce(h.response.map(r => typeConvert.ChatResponsePart.fromContent(r, this.commands.converter)));
-			res.push(new extHostTypes.ChatResponseTurn(parts, result, { extensionId: '', participant: h.request.agentId }, h.request.command));
+			res.push(new extHostTypes.ChatResponseTurn(parts, result, { extensionId: '', name: h.request.agentId }, h.request.command));
 		}
 
 		return res;
@@ -508,9 +508,11 @@ class ExtHostChatAgent {
 				updateMetadataSoon();
 			},
 			get fullName() {
+				checkProposedApiEnabled(that.extension, 'defaultChatParticipant');
 				return that._fullName ?? that.extension.displayName ?? that.extension.name;
 			},
 			set fullName(v) {
+				checkProposedApiEnabled(that.extension, 'defaultChatParticipant');
 				that._fullName = v;
 				updateMetadataSoon();
 			},
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index 4827cdfbfeb..4fb94e3f1c8 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -4257,7 +4257,7 @@ export class ChatRequestTurn implements vscode.ChatRequestTurn {
 		readonly prompt: string,
 		readonly command: string | undefined,
 		readonly variables: vscode.ChatResolvedVariable[],
-		readonly participant: { extensionId: string; participant: string },
+		readonly participant: { extensionId: string; name: string },
 	) { }
 }
 
@@ -4266,7 +4266,7 @@ export class ChatResponseTurn implements vscode.ChatResponseTurn {
 	constructor(
 		readonly response: ReadonlyArray<ChatResponseMarkdownPart | ChatResponseFileTreePart | ChatResponseAnchorPart | ChatResponseCommandButtonPart>,
 		readonly result: vscode.ChatResult,
-		readonly participant: { extensionId: string; participant: string },
+		readonly participant: { extensionId: string; name: string },
 		readonly command?: string
 	) { }
 }
diff --git a/src/vscode-dts/vscode.proposed.chatParticipant.d.ts b/src/vscode-dts/vscode.proposed.chatParticipant.d.ts
index ed62261761d..5fcc77cb7b5 100644
--- a/src/vscode-dts/vscode.proposed.chatParticipant.d.ts
+++ b/src/vscode-dts/vscode.proposed.chatParticipant.d.ts
@@ -23,7 +23,7 @@ declare module 'vscode' {
 		/**
 		 * The name of the chat participant and contributing extension to which this request was directed.
 		 */
-		readonly participant: { readonly extensionId: string; readonly participant: string };
+		readonly participant: { readonly extensionId: string; readonly name: string };
 
 		/**
 		 * The name of the {@link ChatCommand command} that was selected for this request.
@@ -35,7 +35,7 @@ declare module 'vscode' {
 		 */
 		readonly variables: ChatResolvedVariable[];
 
-		private constructor(prompt: string, command: string | undefined, variables: ChatResolvedVariable[], participant: { extensionId: string; participant: string });
+		private constructor(prompt: string, command: string | undefined, variables: ChatResolvedVariable[], participant: { extensionId: string; name: string });
 	}
 
 	/**
@@ -56,14 +56,14 @@ declare module 'vscode' {
 		/**
 		 * The name of the chat participant and contributing extension that this response came from.
 		 */
-		readonly participant: { readonly extensionId: string; readonly participant: string };
+		readonly participant: { readonly extensionId: string; readonly name: string };
 
 		/**
 		 * The name of the command that this response came from.
 		 */
 		readonly command?: string;
 
-		private constructor(response: ReadonlyArray<ChatResponseMarkdownPart | ChatResponseFileTreePart | ChatResponseAnchorPart | ChatResponseCommandButtonPart>, result: ChatResult, participant: { extensionId: string; participant: string });
+		private constructor(response: ReadonlyArray<ChatResponseMarkdownPart | ChatResponseFileTreePart | ChatResponseAnchorPart | ChatResponseCommandButtonPart>, result: ChatResult, participant: { extensionId: string; name: string });
 	}
 
 	export interface ChatContext {
@@ -239,16 +239,10 @@ declare module 'vscode' {
 		 */
 		readonly name: string;
 
-		/**
-		 * The full name of this participant.
-		 * TODO@API This is only used for the default participant, but it seems useful, so should we keep it so we can use it in the future?
-		 */
-		fullName: string;
-
 		/**
 		 * A human-readable description explaining what this participant does.
 		 */
-		description: string;
+		description?: string;
 
 		/**
 		 * Icon for the participant shown in UI.
diff --git a/src/vscode-dts/vscode.proposed.defaultChatParticipant.d.ts b/src/vscode-dts/vscode.proposed.defaultChatParticipant.d.ts
index e1c026a6557..07a2b6f5c42 100644
--- a/src/vscode-dts/vscode.proposed.defaultChatParticipant.d.ts
+++ b/src/vscode-dts/vscode.proposed.defaultChatParticipant.d.ts
@@ -18,6 +18,11 @@ declare module 'vscode' {
 		 */
 		isDefault?: boolean;
 
+		/**
+		 * The full name of this participant.
+		 */
+		fullName?: string;
+
 		/**
 		 * When true, this participant is invoked when the user submits their query using ctrl/cmd+enter
 		 * TODO@API name