fix: Support pagination in tools change handler

Author: pantanurag555

mcp/src/main/java/io/modelcontextprotocol/client/McpAsyncClient.java

@@ -682,9 +682,17 @@ public Mono<McpSchema.ListToolsResult> listTools(String cursor) {
 	private NotificationHandler asyncToolsChangeNotificationHandler(
 			List<Function<List<McpSchema.Tool>, Mono<Void>>> toolsChangeConsumers) {
 		// TODO: params are not used yet
-		return params -> this.listTools()
-			.flatMap(listToolsResult -> Flux.fromIterable(toolsChangeConsumers)
-				.flatMap(consumer -> consumer.apply(listToolsResult.tools()))
+		return params -> this.listTools().expand(result -> {
+			if (result.nextCursor() != null) {
+				return this.listTools(result.nextCursor());
+			}
+			return Mono.empty();
+		}).reduce(new ArrayList<McpSchema.Tool>(), (allTools, result) -> {
+			allTools.addAll(result.tools());
+			return allTools;
+		})
+			.flatMap(allTools -> Flux.fromIterable(toolsChangeConsumers)
+				.flatMap(consumer -> consumer.apply(allTools))
 				.onErrorResume(error -> {
 					logger.error("Error handling tools list change notification", error);
 					return Mono.empty();

mcp/src/test/java/io/modelcontextprotocol/client/McpAsyncClientResponseHandlerTests.java

@@ -17,6 +17,7 @@
 import io.modelcontextprotocol.spec.McpSchema;
 import io.modelcontextprotocol.spec.McpSchema.ClientCapabilities;
 import io.modelcontextprotocol.spec.McpSchema.InitializeResult;
+import io.modelcontextprotocol.spec.McpSchema.PaginatedRequest;
 import io.modelcontextprotocol.spec.McpSchema.Root;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -109,27 +110,52 @@ void testToolsChangeNotificationHandling() throws JsonProcessingException {
 
 		// Create a mock tools list that the server will return
 		Map<String, Object> inputSchema = Map.of("type", "object", "properties", Map.of(), "required", List.of());
-		McpSchema.Tool mockTool = new McpSchema.Tool("test-tool", "Test Tool Description",
+		McpSchema.Tool mockTool = new McpSchema.Tool("test-tool-1", "Test Tool 1 Description",
 				new ObjectMapper().writeValueAsString(inputSchema));
-		McpSchema.ListToolsResult mockToolsResult = new McpSchema.ListToolsResult(List.of(mockTool), null);
+
+		// Create page 1 response with nextPageToken
+		String nextPageToken = "page2Token";
+		McpSchema.ListToolsResult mockToolsResult1 = new McpSchema.ListToolsResult(List.of(mockTool), nextPageToken);
 
 		// Simulate server sending tools/list_changed notification
 		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(McpSchema.JSONRPC_VERSION,
 				McpSchema.METHOD_NOTIFICATION_TOOLS_LIST_CHANGED, null);
 		transport.simulateIncomingMessage(notification);
 
-		// Simulate server response to tools/list request
-		McpSchema.JSONRPCRequest toolsListRequest = transport.getLastSentMessageAsRequest();
-		assertThat(toolsListRequest.method()).isEqualTo(McpSchema.METHOD_TOOLS_LIST);
+		// Simulate server response to first tools/list request
+		McpSchema.JSONRPCRequest toolsListRequest1 = transport.getLastSentMessageAsRequest();
+		assertThat(toolsListRequest1.method()).isEqualTo(McpSchema.METHOD_TOOLS_LIST);
+
+		McpSchema.JSONRPCResponse toolsListResponse1 = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
+				toolsListRequest1.id(), mockToolsResult1, null);
+		transport.simulateIncomingMessage(toolsListResponse1);
+
+		// Create mock tools for page 2
+		McpSchema.Tool mockTool2 = new McpSchema.Tool("test-tool-2", "Test Tool 2 Description",
+				new ObjectMapper().writeValueAsString(inputSchema));
+
+		// Create page 2 response with no nextPageToken (last page)
+		McpSchema.ListToolsResult mockToolsResult2 = new McpSchema.ListToolsResult(List.of(mockTool2), null);
+
+		// Simulate server response to second tools/list request with page token
+		McpSchema.JSONRPCRequest toolsListRequest2 = transport.getLastSentMessageAsRequest();
+		assertThat(toolsListRequest2.method()).isEqualTo(McpSchema.METHOD_TOOLS_LIST);
+
+		// Verify the page token was included in the request
+		PaginatedRequest params = (PaginatedRequest) toolsListRequest2.params();
+		assertThat(params).isNotNull();
+		assertThat(params.cursor()).isEqualTo(nextPageToken);
 
-		McpSchema.JSONRPCResponse toolsListResponse = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
-				toolsListRequest.id(), mockToolsResult, null);
-		transport.simulateIncomingMessage(toolsListResponse);
+		McpSchema.JSONRPCResponse toolsListResponse2 = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
+				toolsListRequest2.id(), mockToolsResult2, null);
+		transport.simulateIncomingMessage(toolsListResponse2);
 
-		// Verify the consumer received the expected tools
-		assertThat(receivedTools).hasSize(1);
-		assertThat(receivedTools.get(0).name()).isEqualTo("test-tool");
-		assertThat(receivedTools.get(0).description()).isEqualTo("Test Tool Description");
+		// Verify the consumer received all expected tools from both pages
+		assertThat(receivedTools).hasSize(2);
+		assertThat(receivedTools.get(0).name()).isEqualTo("test-tool-1");
+		assertThat(receivedTools.get(0).description()).isEqualTo("Test Tool 1 Description");
+		assertThat(receivedTools.get(1).name()).isEqualTo("test-tool-2");
+		assertThat(receivedTools.get(1).description()).isEqualTo("Test Tool 2 Description");
 
 		asyncMcpClient.closeGracefully();
 	}