Fix a robust parsing issue in KimiK2ToolParser that causes IndexError (#27565)

Signed-off-by: wangln19 <wanglinian@dev.wanglinian.msh-dev.svc.cluster.local>
Co-authored-by: wangln19 <wanglinian@dev.wanglinian.msh-dev.svc.cluster.local>

tests/tool_use/test_kimi_k2_tool_parser.py

@@ -37,11 +37,11 @@ def assert_tool_calls(
         assert actual_tool_call.type == "function"
         assert actual_tool_call.function == expected_tool_call.function
 
-        # assert tool call id format
-        assert actual_tool_call.id.startswith("functions.")
+        # assert tool call id format: should contain function name and numeric index
+        # Format can be either "functions.func_name:0" or "func_name:0"
         assert actual_tool_call.id.split(":")[-1].isdigit()
         assert (
-            actual_tool_call.id.split(".")[1].split(":")[0]
+            actual_tool_call.id.split(":")[0].split(".")[-1]
             == expected_tool_call.function.name
         )
 

vllm/entrypoints/openai/tool_parsers/kimi_k2_tool_parser.py

@@ -96,8 +96,8 @@ class KimiK2ToolParser(ToolParser):
                 tool_calls = []
                 for match in function_call_tuples:
                     function_id, function_args = match
-                    # function_id: functions.get_weather:0
-                    function_name = function_id.split(".")[1].split(":")[0]
+                    # function_id: functions.get_weather:0 or get_weather:0
+                    function_name = function_id.split(":")[0].split(".")[-1]
                     tool_calls.append(
                         ToolCall(
                             id=function_id,
@@ -254,7 +254,7 @@ class KimiK2ToolParser(ToolParser):
                 )
                 if current_tool_call_matches:
                     tool_id, tool_args = current_tool_call_matches.groups()
-                    tool_name = tool_id.split(".")[1].split(":")[0]
+                    tool_name = tool_id.split(":")[0].split(".")[-1]
                     current_tool_call["id"] = tool_id
                     current_tool_call["name"] = tool_name
                     current_tool_call["arguments"] = tool_args
@@ -264,7 +264,7 @@ class KimiK2ToolParser(ToolParser):
                     )
                     if current_tool_call_name_matches:
                         (tool_id_str,) = current_tool_call_name_matches.groups()
-                        tool_name = tool_id_str.split(".")[1].split(":")[0]
+                        tool_name = tool_id_str.split(":")[0].split(".")[-1]
                         current_tool_call["id"] = tool_id_str
                         current_tool_call["name"] = tool_name
                         current_tool_call["arguments"] = ""