[BUG] Handle escaped JSON in tool call arguments (#56)

* Handle escaped JSON in tool call arguments

Handle escaped JSON in tool call arguments. Fix issue #52.

* Handle JSON decode errors in tool call parsing

Adds error handling for JSONDecodeError when parsing tool call results. If the string is not valid JSON, it is retained as a string instead of raising an exception.

Author: paxiaatucsdedu

libs/oci/langchain_oci/chat_models/oci_generative_ai.py

@@ -94,9 +94,19 @@ def remove_signature_from_tool_description(name: str, description: str) -> str:
     @staticmethod
     def convert_oci_tool_call_to_langchain(tool_call: Any) -> ToolCall:
         """Convert an OCI tool call to a LangChain ToolCall."""
+        parsed = json.loads(tool_call.arguments)
+
+        # If the parsed result is a string, it means the JSON was escaped, so parse again
+        if isinstance(parsed, str):
+            try:
+                parsed = json.loads(parsed)
+            except json.JSONDecodeError:
+                # If it's not valid JSON, keep it as a string
+                pass
+
         return ToolCall(
             name=tool_call.name,
-            args=json.loads(tool_call.arguments)
+            args=parsed
             if "arguments" in tool_call.attribute_map
             else tool_call.parameters,
             id=tool_call.id if "id" in tool_call.attribute_map else uuid.uuid4().hex[:],

libs/oci/tests/unit_tests/chat_models/test_oci_generative_ai.py

@@ -253,6 +253,67 @@ def get_weather(location: str) -> str:
             assert tool_call["type"] == "function"
             assert tool_call["function"]["name"] == "get_weather"
 
+    # Test escaped JSON arguments (issue #52)
+    def mocked_response_escaped(*args, **kwargs):  # type: ignore[no-untyped-def]
+        """Mock response with escaped JSON arguments."""
+        return MockResponseDict(
+            {
+                "status": 200,
+                "data": MockResponseDict(
+                    {
+                        "chat_response": MockResponseDict(
+                            {
+                                "choices": [
+                                    MockResponseDict(
+                                        {
+                                            "message": MockResponseDict(
+                                                {
+                                                    "content": [
+                                                        MockResponseDict({"text": ""})
+                                                    ],
+                                                    "tool_calls": [
+                                                        MockResponseDict(
+                                                            {
+                                                                "type": "FUNCTION",
+                                                                "id": "call_escaped",
+                                                                "name": "get_weather",
+                                                                # Escaped JSON (the bug scenario)
+                                                                "arguments": '"{\\\"location\\\": \\\"San Francisco\\\"}"',
+                                                                "attribute_map": {
+                                                                    "id": "id",
+                                                                    "type": "type",
+                                                                    "name": "name",
+                                                                    "arguments": "arguments",
+                                                                },
+                                                            }
+                                                        )
+                                                    ],
+                                                }
+                                            ),
+                                            "finish_reason": "tool_calls",
+                                        }
+                                    )
+                                ],
+                                "time_created": "2025-10-22T19:48:12.726000+00:00",
+                            }
+                        ),
+                        "model_id": "meta.llama-3-70b-instruct",
+                        "model_version": "1.0.0",
+                    }
+                ),
+                "request_id": "test_escaped",
+                "headers": MockResponseDict({"content-length": "366"}),
+            }
+        )
+
+    monkeypatch.setattr(llm.client, "chat", mocked_response_escaped)
+    response_escaped = llm.bind_tools(tools=[get_weather]).invoke(messages)
+
+    # Verify escaped JSON was correctly parsed to a dict
+    assert len(response_escaped.tool_calls) == 1
+    assert response_escaped.tool_calls[0]["name"] == "get_weather"
+    assert response_escaped.tool_calls[0]["args"] == {"location": "San Francisco"}
+
 
 @pytest.mark.requires("oci")
 def test_cohere_tool_choice_validation(monkeypatch: MonkeyPatch) -> None: