diff --git a/dap-gateway/src/main/java/io/shinhanlife/dap/mcg/service/ExecuteService.java b/dap-gateway/src/main/java/io/shinhanlife/dap/mcg/service/ExecuteService.java
index a27d2d64..1e5a2cf8 100644
--- a/dap-gateway/src/main/java/io/shinhanlife/dap/mcg/service/ExecuteService.java
+++ b/dap-gateway/src/main/java/io/shinhanlife/dap/mcg/service/ExecuteService.java
@@ -262,9 +262,10 @@ public class ExecuteService {
                     headers.put("trace-id", context.requestId());
                     headers.put("request-id", java.util.UUID.randomUUID().toString());
                     String apiKey = properties.toolServerApiKey();
-                    if (apiKey != null && !apiKey.isEmpty()) {
-                        headers.put("X-Tool-Server-API-Key", apiKey);
+                    if (apiKey == null || apiKey.isEmpty()) {
+                        apiKey = "tool-server-key";
                     }
+                    headers.put("X-Tool-Server-API-Key", apiKey);
                     
                     ObjectNode pageArguments = paginationValidator.normalize(metadata, arguments);
                     LargeToolResponseService.Collector collector = largeResponses.newCollector(metadata.getName(), context.requestId());