diff --git a/packages/components/nodes/tools/CustomTool/core.ts b/packages/components/nodes/tools/CustomTool/core.ts
index 86addc6b130..786ad6f7d01 100644
--- a/packages/components/nodes/tools/CustomTool/core.ts
+++ b/packages/components/nodes/tools/CustomTool/core.ts
@@ -96,6 +96,9 @@ export class DynamicStructuredTool<
             await runManager?.handleToolError(e)
             throw e
         }
+        if (result && typeof result !== 'string') {
+            result = JSON.stringify(result)
+        }
         await runManager?.handleToolEnd(result)
         return result
     }