fix: normalize MCP object schemas without properties

tests/tools/test_mcp_tool.py

@@ -106,6 +106,18 @@ class TestSchemaConversion:
         assert schema["parameters"]["type"] == "object"
         assert schema["parameters"]["properties"] == {}
 
+    def test_object_schema_without_properties_gets_normalized(self):
+        from tools.mcp_tool import _convert_mcp_schema
+
+        mcp_tool = _make_mcp_tool(
+            name="ask",
+            description="Ask Crawl4AI",
+            input_schema={"type": "object"},
+        )
+        schema = _convert_mcp_schema("crawl4ai", mcp_tool)
+
+        assert schema["parameters"] == {"type": "object", "properties": {}}
+
     def test_tool_name_prefix_format(self):
         from tools.mcp_tool import _convert_mcp_schema
 
@@ -1893,6 +1905,33 @@ class TestSamplingCallbackText:
         messages = call_args.kwargs["messages"]
         assert messages[0] == {"role": "system", "content": "Be helpful"}
 
+    def test_server_tools_with_object_schema_are_normalized(self):
+        """Server-provided tools should gain empty properties for object schemas."""
+        fake_client = MagicMock()
+        fake_client.chat.completions.create.return_value = _make_llm_response()
+        server_tool = SimpleNamespace(
+            name="ask",
+            description="Ask Crawl4AI",
+            inputSchema={"type": "object"},
+        )
+
+        with patch(
+            "agent.auxiliary_client.call_llm",
+            return_value=fake_client.chat.completions.create.return_value,
+        ) as mock_call:
+            params = _make_sampling_params(tools=[server_tool])
+            asyncio.run(self.handler(None, params))
+
+        tools = mock_call.call_args.kwargs["tools"]
+        assert tools == [{
+            "type": "function",
+            "function": {
+                "name": "ask",
+                "description": "Ask Crawl4AI",
+                "parameters": {"type": "object", "properties": {}},
+            },
+        }]
+
     def test_length_stop_reason(self):
         """finish_reason='length' maps to stopReason='maxTokens'."""
         fake_client = MagicMock()

tools/mcp_tool.py

@@ -605,7 +605,9 @@ class SamplingHandler:
                     "function": {
                         "name": getattr(t, "name", ""),
                         "description": getattr(t, "description", "") or "",
-                        "parameters": getattr(t, "inputSchema", {}) or {},
+                        "parameters": _normalize_mcp_input_schema(
+                            getattr(t, "inputSchema", None)
+                        ),
                     },
                 }
                 for t in server_tools
@@ -1213,6 +1215,17 @@ def _make_check_fn(server_name: str):
 # Discovery & registration
 # ---------------------------------------------------------------------------
 
+def _normalize_mcp_input_schema(schema: dict | None) -> dict:
+    """Normalize MCP input schemas for LLM tool-calling compatibility."""
+    if not schema:
+        return {"type": "object", "properties": {}}
+
+    if schema.get("type") == "object" and "properties" not in schema:
+        return {**schema, "properties": {}}
+
+    return schema
+
+
 def _convert_mcp_schema(server_name: str, mcp_tool) -> dict:
     """Convert an MCP tool listing to the Hermes registry schema format.
 
@@ -1231,10 +1244,7 @@ def _convert_mcp_schema(server_name: str, mcp_tool) -> dict:
     return {
         "name": prefixed_name,
         "description": mcp_tool.description or f"MCP tool {mcp_tool.name} from {server_name}",
-        "parameters": mcp_tool.inputSchema if mcp_tool.inputSchema else {
-            "type": "object",
-            "properties": {},
-        },
+        "parameters": _normalize_mcp_input_schema(mcp_tool.inputSchema),
     }