feat: Add BalanceService tool for checking account balance

axhub-tool-other/src/main/java/io/shinhanlife/axhub/biz/mcp/tool/balance/dto/BalanceReq.java

@@ -0,0 +1,10 @@
+package io.shinhanlife.axhub.biz.mcp.tool.balance.dto;
+
+import io.shinhanlife.axhub.biz.mcp.tool.annotation.McpParameter;
+import lombok.Data;
+
+@Data
+public class BalanceReq {
+    @McpParameter(description = "고객의 계좌번호 (- 제외)", required = true)
+    private String accountNumber;
+}

axhub-tool-other/src/main/java/io/shinhanlife/axhub/biz/mcp/tool/balance/dto/BalanceRes.java

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+package io.shinhanlife.axhub.biz.mcp.tool.balance.dto;
+
+import lombok.Data;
+
+@Data
+public class BalanceRes {
+    private String status;
+    private String message;
+    private String accountNumber;
+    private long balance;
+}

axhub-tool-other/src/main/java/io/shinhanlife/axhub/biz/mcp/tool/balance/service/BalanceService.java

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+package io.shinhanlife.axhub.biz.mcp.tool.balance.service;
+
+import io.shinhanlife.axhub.biz.mcp.tool.annotation.McpFunction;
+import io.shinhanlife.axhub.biz.mcp.tool.annotation.McpTool;
+import io.shinhanlife.axhub.biz.mcp.tool.balance.dto.BalanceReq;
+import io.shinhanlife.axhub.biz.mcp.tool.service.AbstractMcpToolService;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+import java.util.Map;
+
+@Slf4j
+@Service
+@McpTool(routingType = "MCI", group = "COMMON")
+public class BalanceService extends AbstractMcpToolService {
+
+    @McpFunction(
+        name = "balance",
+        description = "고객의 계좌 잔액을 조회합니다.",
+        prompt = "고객 계좌 잔액을 조회해줘.",
+        mappingId = "ACC_001"
+    )
+    public Object execute(BalanceReq req) {
+        log.info("[Balance] 계좌 잔액 조회 요청 수신. 계좌번호: {}", req.getAccountNumber());
+        
+        // 레거시 연동
+        Map<String, Object> result = executeLegacy("MCI", "ACC_001", req);
+        
+        // 가짜 데이터 응답 매핑 (AI 에이전트가 그럴듯하게 보여주기 위함)
+        if ("SUCCESS".equals(result.get("status"))) {
+            result.put("accountNumber", req.getAccountNumber());
+            result.put("balance", 1520300); // 1,520,300원 (가상의 잔액)
+            result.put("currency", "KRW");
+            result.put("message", "잔액 조회가 완료되었습니다.");
+        }
+        
+        return result;
+    }
+}