Fix tool used error message not proper escaped in MLChatAgentRunner

common/src/test/java/org/opensearch/ml/common/utils/StringUtilsTest.java

@@ -1225,4 +1225,46 @@ public void testDeserializeNullFloat_ToNull() {
         assertTrue(m.get("fPrim").isJsonPrimitive());
         assertEquals(1.0f, m.get("fPrim").getAsFloat(), 1e-9f);
     }
+
+    @Test
+    public void testProcessTextDoc_ExceptionMessageEscaping() {
+        // Test the problematic exception message from the error
+        String problematicMessage = "Invalid payload: { \"system\": [{\"text\": \"You are a precise...\"}], \"messages\": [...] }\n"
+            + "See https://github.com/google/gson/blob/main/Troubleshooting.md#unexpected-json-structure";
+
+        String escapedMessage = StringUtils.processTextDoc(problematicMessage);
+
+        // Verify that problematic characters are escaped
+        assertFalse(
+            "Escaped message should not contain unescaped newlines",
+            escapedMessage.contains("\n") && !escapedMessage.contains("\\n")
+        );
+        assertFalse(
+            "Escaped message should not contain unescaped quotes",
+            escapedMessage.contains("\"") && !escapedMessage.contains("\\\"")
+        );
+    }
+
+    @Test
+    public void testProcessTextDoc_GsonParsingErrorMessageEscaping() {
+        // Test the specific Gson error message pattern
+        String gsonError = "Expected BEGIN_ARRAY but was STRING at line 1 column 1 path $\n"
+            + "See https://github.com/google/gson/blob/main/Troubleshooting.md#unexpected-json-structure";
+
+        String escapedMessage = StringUtils.processTextDoc(gsonError);
+
+        // The escaped message should be safe for JSON inclusion
+        assertTrue("Escaped message should be safe for JSON", !escapedMessage.contains("\n") || escapedMessage.contains("\\n"));
+    }
+
+    @Test
+    public void testProcessTextDoc_NormalMessagePassthrough() {
+        // Test that normal messages without special characters pass through unchanged
+        String normalMessage = "Tool execution failed with normal error";
+
+        String escapedMessage = StringUtils.processTextDoc(normalMessage);
+
+        // Normal messages should be handled properly
+        assertTrue("Normal messages should be handled properly", escapedMessage.length() > 0);
+    }
 }

ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunner.java

@@ -625,7 +625,13 @@ private static void runTool(
                         .add(
                             substitute(
                                 tmpParameters.get(INTERACTION_TEMPLATE_TOOL_RESPONSE),
-                                Map.of(TOOL_CALL_ID, toolCallId, "tool_response", "Tool " + action + " failed: " + e.getMessage()),
+                                Map
+                                    .of(
+                                        TOOL_CALL_ID,
+                                        toolCallId,
+                                        "tool_response",
+                                        "Tool " + action + " failed: " + processTextDoc(e.getMessage())
+                                    ),
                                 INTERACTIONS_PREFIX
                             )
                         );

ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/agent/MLChatAgentRunnerTest.java

@@ -691,6 +691,38 @@ public void testToolThrowException() {
         assertNotNull(modelTensorOutput);
     }
 
+    @Test
+    public void testToolExceptionMessageEscaping() {
+        // Mock tool validation to return true
+        when(firstTool.validate(any())).thenReturn(true);
+
+        // Create an MLAgent with tools
+        MLAgent mlAgent = createMLAgentWithTools();
+
+        // Create parameters for the agent
+        Map<String, String> params = createAgentParamsWithAction(FIRST_TOOL, "someInput");
+
+        // Mock tool to throw exception with problematic characters (quotes, newlines)
+        String problematicMessage = "Invalid payload: { \"system\": [{\"text\": \"You are a precise...\"}] }\n" +
+                "See https://github.com/google/gson/blob/main/Troubleshooting.md#unexpected-json-structure";
+
+        Mockito
+                .doThrow(new IllegalArgumentException(problematicMessage))
+                .when(firstTool)
+                .run(Mockito.anyMap(), toolListenerCaptor.capture());
+
+        // Run the MLChatAgentRunner
+        mlChatAgentRunner.run(mlAgent, params, agentActionListener, null);
+
+        // Verify that the tool's run method was called
+        verify(firstTool).run(any(), any());
+
+        // Verify that the agent completes without throwing JSON parsing exceptions
+        Mockito.verify(agentActionListener).onResponse(objectCaptor.capture());
+        ModelTensorOutput modelTensorOutput = (ModelTensorOutput) objectCaptor.getValue();
+        assertNotNull("Agent should complete successfully even with problematic exception messages", modelTensorOutput);
+    }
+
     @Test
     public void testToolParameters() {
         // Mock tool validation to return false.