feat: use MCP SDK for tool pod calls

dap-gateway/src/main/java/io/shinhanlife/dap/mcg/service/ExecuteService.java

@@ -261,7 +261,6 @@ public class ExecuteService {
                     if (metadata.getPodUrl() != null && !metadata.getPodUrl().isEmpty()) {
                         targetUrl = metadata.getPodUrl();
                     }
-                    String executeApiUrl = targetUrl + "/mcp/" + metadata.getName();
                     
                     Map<String, String> headers = new java.util.HashMap<>();
                     headers.put("trace-id", context.requestId());
@@ -279,16 +278,16 @@ public class ExecuteService {
                         
                         JsonNode data = null;
                         try {
-                            data = toolInvoker.invoke(pagePayload, executeApiUrl, headers);
+                            data = toolInvoker.invoke(metadata.getName(), pagePayload, targetUrl, headers);
                         } catch (org.springframework.web.client.RestClientResponseException e) {
                             // HTTP 4xx, 5xx 에러는 연결 오류가 아니라 비즈니스 로직 오류이거나 검증 실패이므로 원본 에러를 그대로 반환
                             throw new ToolExecutionException(FailureType.SERVER_ERROR, "Tool Pod HTTP 에러 (" + e.getStatusCode() + "): " + e.getResponseBodyAsString());
                         } catch (Exception e) {
-                            if (executeApiUrl.contains("http://tool-")) {
-                                String fallbackUrl = executeApiUrl.replaceAll("http://tool-[a-zA-Z0-9-]+", "http://localhost");
+                            if (targetUrl.contains("http://tool-")) {
+                                String fallbackUrl = targetUrl.replaceAll("http://tool-[a-zA-Z0-9-]+", "http://localhost");
                                 log.warn(" [ExecuteService] 호스트를 찾을 수 없어 localhost로 재시도합니다: {}", fallbackUrl);
                                 try {
-                                    data = toolInvoker.invoke(pagePayload, fallbackUrl, headers);
+                                    data = toolInvoker.invoke(metadata.getName(), pagePayload, fallbackUrl, headers);
                                 } catch (Exception ex) {
                                     throw new ToolExecutionException(FailureType.SERVER_ERROR, "Tool Pod 호출 실패 (localhost 재시도 포함): " + ex.getMessage());
                                 }
@@ -385,4 +384,4 @@ public class ExecuteService {
     public void shutdown() {
         executor.shutdownNow();
     }
-}
+}

dap-gateway/src/main/java/io/shinhanlife/dap/mcg/transport/HttpToolInvoker.java

@@ -1,69 +1,81 @@
 package io.shinhanlife.dap.mcg.transport;
 
-
-/**
- * @package io.shinhanlife.dap.mcg.transport
- * @className HttpToolInvoker
- * @description AX HUB 시스템 처리 클래스
- * @author 0986406
- * @create 2026.09.01
- * <pre>
- * ---------- 개정이력 ----------
- * 수정일      수정자    수정내용
- * ---------- -------- ---------------------------
- * 2026.09.01  0986406    최초생성
- * 
- * </pre>
- */
-import io.shinhanlife.dap.mcg.resilience.FailureType;
-import io.shinhanlife.dap.mcg.resilience.ToolExecutionException;
-import org.springframework.http.MediaType;
-import org.springframework.stereotype.Component;
-import org.springframework.web.client.RestClient;
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
-import lombok.extern.slf4j.Slf4j;
-
+import com.fasterxml.jackson.databind.node.TextNode;
+import io.modelcontextprotocol.client.McpClient;
+import io.modelcontextprotocol.client.McpSyncClient;
+import io.modelcontextprotocol.client.transport.HttpClientStreamableHttpTransport;
+import io.modelcontextprotocol.spec.McpSchema;
+import io.shinhanlife.dap.mcg.resilience.FailureType;
+import io.shinhanlife.dap.mcg.resilience.ToolExecutionException;
+import java.net.http.HttpRequest;
+import java.time.Duration;
 import java.util.Map;
-import java.util.UUID;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Component;
 
+/** MCP SDK client used for Gateway-to-Tool-Pod calls over Streamable HTTP. */
 @Slf4j
 @Component
 public class HttpToolInvoker implements ToolInvoker {
 
-    private final RestClient restClient;
     private final ObjectMapper objectMapper;
 
     public HttpToolInvoker(ObjectMapper objectMapper) {
         this.objectMapper = objectMapper;
-        this.restClient = RestClient.create();
     }
 
     @Override
-    public JsonNode invoke(Map<String, Object> payload, String targetUrl, Map<String, String> headers) {
-        try {
-            RestClient.RequestBodySpec requestSpec = restClient.post()
-                    .uri(targetUrl)
-                    .contentType(MediaType.APPLICATION_JSON);
-                    
-            if (headers != null) {
-                headers.forEach(requestSpec::header);
+    public JsonNode invoke(String toolName, Map<String, Object> arguments, String podUrl, Map<String, String> headers) {
+        String endpoint = podUrl.replaceAll("/+$", "") + "/mcp";
+        HttpRequest.Builder requestBuilder = HttpRequest.newBuilder();
+        if (headers != null) {
+            headers.forEach(requestBuilder::header);
+        }
+
+        HttpClientStreamableHttpTransport transport = HttpClientStreamableHttpTransport.builder(endpoint)
+                .requestBuilder(requestBuilder)
+                .connectTimeout(Duration.ofSeconds(5))
+                .build();
+        try (McpSyncClient client = McpClient.sync(transport)
+                .clientInfo(new McpSchema.Implementation("dap-gateway", "1.0.0"))
+                .requestTimeout(Duration.ofSeconds(30))
+                .build()) {
+            client.initialize();
+            McpSchema.CallToolResult result = client.callTool(McpSchema.CallToolRequest.builder()
+                    .name(toolName)
+                    .arguments(arguments)
+                    .build());
+            if (Boolean.TRUE.equals(result.isError())) {
+                throw new ToolExecutionException(FailureType.BUSINESS_ERROR, "Tool Pod MCP error: " + textContent(result));
             }
-            
-            Object httpResult = requestSpec.body(payload)
-                    .retrieve()
-                    .body(Object.class);
-            
-            return extractData(objectMapper.valueToTree(httpResult));
-        } catch (Exception e) {
-            throw new ToolExecutionException(FailureType.SERVER_ERROR, "Tool Pod HTTP 호출 실패: " + e.getMessage(), e);
+            return result.structuredContent() != null
+                    ? objectMapper.valueToTree(result.structuredContent())
+                    : textContentAsJson(result);
+        } catch (ToolExecutionException error) {
+            throw error;
+        } catch (Exception error) {
+            throw new ToolExecutionException(FailureType.SERVER_ERROR,
+                    "Tool Pod MCP call failed: " + error.getMessage(), error);
         }
     }
 
-    private JsonNode extractData(JsonNode root) {
-        if (!root.path("success").asBoolean(true)) {
-            throw new ToolExecutionException(FailureType.BUSINESS_ERROR, "Tool 서버 업무 오류: " + root.path("error").asText());
+    private JsonNode textContentAsJson(McpSchema.CallToolResult result) {
+        String text = textContent(result);
+        try {
+            return objectMapper.readTree(text);
+        } catch (Exception ignored) {
+            return TextNode.valueOf(text);
         }
-        return root.has("data") ? root.get("data") : root;
+    }
+
+    private String textContent(McpSchema.CallToolResult result) {
+        return result.content().stream()
+                .filter(McpSchema.TextContent.class::isInstance)
+                .map(McpSchema.TextContent.class::cast)
+                .map(McpSchema.TextContent::text)
+                .findFirst()
+                .orElse("");
     }
 }

dap-gateway/src/main/java/io/shinhanlife/dap/mcg/transport/ToolInvoker.java

@@ -22,5 +22,5 @@ import java.util.Map;
  * Tool 서버 호출 transport의 최소 공통 인터페이스입니다.
  */
 public interface ToolInvoker {
-    JsonNode invoke(Map<String, Object> payload, String targetUrl, Map<String, String> headers);
+    JsonNode invoke(String toolName, Map<String, Object> arguments, String podUrl, Map<String, String> headers);
 }