diff --git a/core/src/main/java/com/google/adk/tools/mcp/ConversionUtils.java b/core/src/main/java/com/google/adk/tools/mcp/ConversionUtils.java
index e0f9eb1ff..8ad7d1b46 100644
--- a/core/src/main/java/com/google/adk/tools/mcp/ConversionUtils.java
+++ b/core/src/main/java/com/google/adk/tools/mcp/ConversionUtils.java
@@ -19,19 +19,26 @@
 import com.google.adk.tools.BaseTool;
 import com.google.genai.types.FunctionDeclaration;
 import com.google.genai.types.Schema;
+import io.modelcontextprotocol.json.McpJsonMapper;
 import io.modelcontextprotocol.spec.McpSchema;
 import java.util.Optional;
 
 /** Utility class for converting between different representations of MCP tools. */
 public final class ConversionUtils {
 
+  private static final McpJsonMapper jsonMapper = McpJsonMapper.getDefault();
+
   public McpSchema.Tool adkToMcpToolType(BaseTool tool) {
     Optional<FunctionDeclaration> toolDeclaration = tool.declaration();
     if (toolDeclaration.isEmpty()) {
-      return new McpSchema.Tool(tool.name(), tool.description(), "");
+      return McpSchema.Tool.builder().name(tool.name()).description(tool.description()).build();
     }
     Schema geminiSchema = toolDeclaration.get().parameters().get();
-    return new McpSchema.Tool(tool.name(), tool.description(), geminiSchema.toJson());
+    return McpSchema.Tool.builder()
+        .name(tool.name())
+        .description(tool.description())
+        .inputSchema(jsonMapper, geminiSchema.toJson())
+        .build();
   }
 
   private ConversionUtils() {}
diff --git a/core/src/main/java/com/google/adk/tools/mcp/DefaultMcpTransportBuilder.java b/core/src/main/java/com/google/adk/tools/mcp/DefaultMcpTransportBuilder.java
index 3e3e4c157..b82ebae84 100644
--- a/core/src/main/java/com/google/adk/tools/mcp/DefaultMcpTransportBuilder.java
+++ b/core/src/main/java/com/google/adk/tools/mcp/DefaultMcpTransportBuilder.java
@@ -5,6 +5,7 @@
 import io.modelcontextprotocol.client.transport.HttpClientStreamableHttpTransport;
 import io.modelcontextprotocol.client.transport.ServerParameters;
 import io.modelcontextprotocol.client.transport.StdioClientTransport;
+import io.modelcontextprotocol.json.McpJsonMapper;
 import io.modelcontextprotocol.spec.McpClientTransport;
 import java.util.Collection;
 import java.util.Optional;
@@ -17,10 +18,12 @@
  */
 public class DefaultMcpTransportBuilder implements McpTransportBuilder {
 
+  private static final McpJsonMapper jsonMapper = McpJsonMapper.getDefault();
+
   @Override
   public McpClientTransport build(Object connectionParams) {
     if (connectionParams instanceof ServerParameters serverParameters) {
-      return new StdioClientTransport(serverParameters);
+      return new StdioClientTransport(serverParameters, jsonMapper);
     } else if (connectionParams instanceof SseServerParameters sseServerParams) {
       return HttpClientSseClientTransport.builder(sseServerParams.url())
           .sseEndpoint(
@@ -42,8 +45,9 @@ public McpClientTransport build(Object connectionParams) {
     } else if (connectionParams instanceof StreamableHttpServerParameters streamableParams) {
       return HttpClientStreamableHttpTransport.builder(streamableParams.url())
           .connectTimeout(streamableParams.timeout())
+          .jsonMapper(jsonMapper)
           .asyncHttpRequestCustomizer(
-              (builder, method, uri, body) -> {
+              (builder, method, uri, body, context) -> {
                 streamableParams.headers().forEach((key, value) -> builder.header(key, value));
                 return Mono.just(builder);
               })
diff --git a/core/src/test/java/com/google/adk/tools/mcp/McpToolsetTest.java b/core/src/test/java/com/google/adk/tools/mcp/McpToolsetTest.java
index 7a780784a..6da5844cb 100644
--- a/core/src/test/java/com/google/adk/tools/mcp/McpToolsetTest.java
+++ b/core/src/test/java/com/google/adk/tools/mcp/McpToolsetTest.java
@@ -31,6 +31,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import io.modelcontextprotocol.client.McpSyncClient;
+import io.modelcontextprotocol.json.McpJsonMapper;
 import io.modelcontextprotocol.spec.McpSchema;
 import java.util.List;
 import java.util.Optional;
@@ -50,6 +51,8 @@ public class McpToolsetTest {
   @Mock private McpSyncClient mockMcpSyncClient;
   @Mock private ReadonlyContext mockReadonlyContext;
 
+  private static final McpJsonMapper jsonMapper = McpJsonMapper.getDefault();
+
   @Test
   public void testMcpToolsetConfig_withStdioServerParams_parsesCorrectly() {
     McpToolsetConfig mcpConfig = new McpToolsetConfig();
@@ -266,11 +269,23 @@ public void testFromConfig_emptyToolFilter_createsToolset() throws Configuration
   public void getTools_withToolFilter_returnsFilteredTools() {
     ImmutableList<String> toolFilter = ImmutableList.of("tool1", "tool3");
     McpSchema.Tool mockTool1 =
-        McpSchema.Tool.builder().name("tool1").description("desc1").inputSchema("{}").build();
+        McpSchema.Tool.builder()
+            .name("tool1")
+            .description("desc1")
+            .inputSchema(jsonMapper, "{}")
+            .build();
     McpSchema.Tool mockTool2 =
-        McpSchema.Tool.builder().name("tool2").description("desc2").inputSchema("{}").build();
+        McpSchema.Tool.builder()
+            .name("tool2")
+            .description("desc2")
+            .inputSchema(jsonMapper, "{}")
+            .build();
     McpSchema.Tool mockTool3 =
-        McpSchema.Tool.builder().name("tool3").description("desc3").inputSchema("{}").build();
+        McpSchema.Tool.builder()
+            .name("tool3")
+            .description("desc3")
+            .inputSchema(jsonMapper, "{}")
+            .build();
     McpSchema.ListToolsResult mockResult =
         new McpSchema.ListToolsResult(ImmutableList.of(mockTool1, mockTool2, mockTool3), null);
 
diff --git a/core/src/test/java/com/google/adk/tools/mcp/StdioServerParametersTest.java b/core/src/test/java/com/google/adk/tools/mcp/StdioServerParametersTest.java
index ef50ccb02..166665309 100644
--- a/core/src/test/java/com/google/adk/tools/mcp/StdioServerParametersTest.java
+++ b/core/src/test/java/com/google/adk/tools/mcp/StdioServerParametersTest.java
@@ -22,6 +22,7 @@
 import com.google.common.collect.ImmutableMap;
 import io.modelcontextprotocol.client.transport.ServerParameters;
 import io.modelcontextprotocol.client.transport.StdioClientTransport;
+import io.modelcontextprotocol.json.McpJsonMapper;
 import java.lang.reflect.Field;
 import java.util.List;
 import java.util.Map;
@@ -33,6 +34,8 @@
 @RunWith(JUnit4.class)
 public final class StdioServerParametersTest {
 
+  private static final McpJsonMapper jsonMapper = McpJsonMapper.getDefault();
+
   @Test
   public void toServerParameters_withNullArgs_createsValidServerParameters() {
     StdioServerParameters params =
@@ -41,7 +44,7 @@ public void toServerParameters_withNullArgs_createsValidServerParameters() {
     ServerParameters serverParams = params.toServerParameters();
 
     assertThat(serverParams).isNotNull();
-    StdioClientTransport transport = new StdioClientTransport(serverParams);
+    StdioClientTransport transport = new StdioClientTransport(serverParams, jsonMapper);
     assertThat(transport).isNotNull();
   }
 
@@ -53,7 +56,7 @@ public void toServerParameters_withNullEnv_createsValidServerParameters() {
     ServerParameters serverParams = params.toServerParameters();
 
     assertThat(serverParams).isNotNull();
-    StdioClientTransport transport = new StdioClientTransport(serverParams);
+    StdioClientTransport transport = new StdioClientTransport(serverParams, jsonMapper);
     assertThat(transport).isNotNull();
   }
 
@@ -66,7 +69,7 @@ public void toServerParameters_withNonNullArgs_createsValidServerParameters() {
     ServerParameters serverParams = params.toServerParameters();
 
     assertThat(serverParams).isNotNull();
-    StdioClientTransport transport = new StdioClientTransport(serverParams);
+    StdioClientTransport transport = new StdioClientTransport(serverParams, jsonMapper);
     assertThat(transport).isNotNull();
   }
 
@@ -79,7 +82,7 @@ public void toServerParameters_withNonNullEnv_createsValidServerParameters() {
     ServerParameters serverParams = params.toServerParameters();
 
     assertThat(serverParams).isNotNull();
-    StdioClientTransport transport = new StdioClientTransport(serverParams);
+    StdioClientTransport transport = new StdioClientTransport(serverParams, jsonMapper);
     assertThat(transport).isNotNull();
   }
 
@@ -94,7 +97,7 @@ public void toServerParameters_withAllFieldsSet_createsValidServerParameters() {
     ServerParameters serverParams = params.toServerParameters();
 
     assertThat(serverParams).isNotNull();
-    StdioClientTransport transport = new StdioClientTransport(serverParams);
+    StdioClientTransport transport = new StdioClientTransport(serverParams, jsonMapper);
     assertThat(transport).isNotNull();
   }
 
@@ -105,7 +108,7 @@ public void toServerParameters_withOnlyCommand_createsValidServerParameters() {
     ServerParameters serverParams = params.toServerParameters();
 
     assertThat(serverParams).isNotNull();
-    StdioClientTransport transport = new StdioClientTransport(serverParams);
+    StdioClientTransport transport = new StdioClientTransport(serverParams, jsonMapper);
     assertThat(transport).isNotNull();
   }
 
diff --git a/pom.xml b/pom.xml
index 0bac51b2a..09d3f3edf 100644
--- a/pom.xml
+++ b/pom.xml
@@ -42,7 +42,7 @@
     <auto-value.version>1.11.0</auto-value.version>
     <spring-boot.version>3.4.1</spring-boot.version>
     <otel.version>1.49.0</otel.version>
-    <mcp.version>0.11.3</mcp.version>
+    <mcp.version>0.14.0</mcp.version>
     <errorprone.version>2.38.0</errorprone.version>
     <google.genai.version>1.8.0</google.genai.version>
     <protobuf.version>4.32.0</protobuf.version>