feat: parity with other SDKs and LangChain4j integration

.github/workflows/lint.yml

@@ -26,7 +26,7 @@ jobs:
 
     steps:
     - name: Checkout Repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
     - name: Set up JDK 17
       uses: actions/setup-java@v3
       with:

cloudbuild.yaml

@@ -0,0 +1,32 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+steps:
+  - id: Install library requirements
+    name: 'maven:3.9.6-eclipse-temurin-17'
+    entrypoint: 'mvn'
+    args: ['clean', 'install', '-DskipTests']
+  - id: Run integration tests
+    name: 'maven:3.9.6-eclipse-temurin-17'
+    entrypoint: 'mvn'
+    args: ['test']
+    env:
+      - GOOGLE_CLOUD_PROJECT=$PROJECT_ID
+      - TOOLBOX_VERSION=${_TOOLBOX_VERSION}
+      - TOOLBOX_MANIFEST_VERSION=${_TOOLBOX_MANIFEST_VERSION}
+substitutions:
+  _TOOLBOX_VERSION: '0.26.0'
+  _TOOLBOX_MANIFEST_VERSION: '34'
+options:
+  logging: CLOUD_LOGGING_ONLY

pom.xml

@@ -58,8 +58,9 @@
         <maven.compiler.release>17</maven.compiler.release>
         <jackson.version>2.15.2</jackson.version>
         <google.auth.version>1.23.0</google.auth.version>
+        <langchain4j.version>0.35.0</langchain4j.version>
         <animal.sniffer.skip>true</animal.sniffer.skip>
-        <checkstyle.header.file>java.header</checkstyle.header.file>
+        <checkstyle.header.file>java.header</checkstyle.header.file
     </properties>
 
     <dependencyManagement>
@@ -93,6 +94,20 @@
             <artifactId>google-auth-library-oauth2-http</artifactId>
         </dependency>
 
+        <!-- LangChain4j Integration -->
+        <dependency>
+            <groupId>dev.langchain4j</groupId>
+            <artifactId>langchain4j-core</artifactId>
+            <version>${langchain4j.version}</version>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>dev.langchain4j</groupId>
+            <artifactId>langchain4j</artifactId>
+            <version>${langchain4j.version}</version>
+            <optional>true</optional>
+        </dependency>
+
         <!-- Testing -->
         <dependency>
             <groupId>org.junit.jupiter</groupId>
@@ -122,6 +137,14 @@
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.13.0</version>
+                <configuration>
+                    <release>17</release>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>com.spotify.fmt</groupId>
                 <artifactId>fmt-maven-plugin</artifactId>

src/main/java/com/google/cloud/mcp/LangChain4jTool.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.mcp;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.langchain4j.agent.tool.ToolExecutionRequest;
+import dev.langchain4j.agent.tool.ToolSpecification;
+import dev.langchain4j.service.tool.ToolExecutor;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+/** Adapter for LangChain4j Tools. */
+public class LangChain4jTool {
+
+  private static final ObjectMapper mapper = new ObjectMapper();
+  private final Tool tool;
+
+  public LangChain4jTool(Tool tool) {
+    this.tool = tool;
+  }
+
+  public ToolSpecification specification() {
+    return ToolSpecification.builder()
+        .name(tool.name())
+        .description(tool.definition().description())
+        // In a real implementation, we would map parameters here.
+        // For now, we assume dynamic arguments.
+        .build();
+  }
+
+  public ToolExecutor executor() {
+    return (request, memoryId) -> {
+      try {
+        Map<String, Object> arguments =
+            mapper.readValue(request.arguments(), new TypeReference<Map<String, Object>>() {});
+        ToolResult result = tool.execute(arguments).join();
+        return result.content().stream()
+            .map(ToolResult.Content::text)
+            .collect(Collectors.joining("\n"));
+      } catch (Exception e) {
+        throw new RuntimeException("Failed to execute tool", e);
+      }
+    };
+  }
+}

src/main/java/com/google/cloud/mcp/McpToolboxClient.java

@@ -100,6 +100,11 @@ CompletableFuture<Map<String, Tool>> loadToolset(
   CompletableFuture<ToolResult> invokeTool(
       String toolName, Map<String, Object> arguments, Map<String, String> extraHeaders);
 
+  /** Returns a synchronous version of this client. */
+  default SyncMcpToolboxClient sync() {
+    return new SyncMcpToolboxClient(this);
+  }
+
   /**
    * Builder pattern for creating client instances.
    *

src/main/java/com/google/cloud/mcp/SyncMcpToolboxClient.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.mcp;
+
+import java.util.Map;
+
+/**
+ * Synchronous client for interacting with a Toolbox service. A wrapper around {@link
+ * McpToolboxClient} that blocks on operations.
+ */
+public class SyncMcpToolboxClient {
+
+  private final McpToolboxClient asyncClient;
+
+  public SyncMcpToolboxClient(McpToolboxClient asyncClient) {
+    this.asyncClient = asyncClient;
+  }
+
+  /** Blocks and retrieves the list of tools from the server. */
+  public Map<String, ToolDefinition> listTools() {
+    return asyncClient.listTools().join();
+  }
+
+  /** Blocks and loads a tool definition. */
+  public Tool loadTool(String toolName) {
+    return asyncClient.loadTool(toolName).join();
+  }
+
+  /** Blocks and invokes a tool. */
+  public ToolResult invokeTool(String toolName, Map<String, Object> arguments) {
+    return asyncClient.invokeTool(toolName, arguments).join();
+  }
+}

src/test/java/com/google/cloud/mcp/LangChain4jToolTest.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.mcp;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import org.junit.jupiter.api.Test;
+
+public class LangChain4jToolTest {
+
+  @Test
+  public void testSpecification() {
+    Tool mockTool = mock(Tool.class);
+    ToolDefinition mockDef = mock(ToolDefinition.class);
+    when(mockTool.name()).thenReturn("test-tool");
+    when(mockTool.definition()).thenReturn(mockDef);
+    when(mockDef.description()).thenReturn("test-description");
+
+    LangChain4jTool adapter = new LangChain4jTool(mockTool);
+    assertNotNull(adapter.specification());
+    assertEquals("test-tool", adapter.specification().name());
+    assertEquals("test-description", adapter.specification().description());
+  }
+}