From 1e5f9fc661377abf7b35d9291033d8a7626b8b4e Mon Sep 17 00:00:00 2001
From: qbc <qianbingchen.qbc@alibaba-inc.com>
Date: Tue, 12 May 2026 17:28:18 +0800
Subject: [PATCH] fix(mcp): remove title in $defs (#1594)

---
 src/agentscope/_utils/_common.py | 9 +++++++++
 tests/toolkit_basic_test.py      | 4 ----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/agentscope/_utils/_common.py b/src/agentscope/_utils/_common.py
index 4c8d83cc66..8a13a1b7e8 100644
--- a/src/agentscope/_utils/_common.py
+++ b/src/agentscope/_utils/_common.py
@@ -257,6 +257,15 @@ def _remove_title_field(schema: dict) -> None:
             schema["additionalProperties"],
         )
 
+    # $defs — referenced sub-schemas, e.g. Pydantic models used as parameter
+    # types generate "$defs": {"SubModel": {"title": "SubModel", ...}}.
+    # These titles are auto-generated noise just like property titles, and
+    # should be removed for the same reason.
+    if "$defs" in schema and isinstance(schema["$defs"], dict):
+        for def_schema in schema["$defs"].values():
+            if isinstance(def_schema, dict):
+                _remove_title_field(def_schema)
+
 
 def _create_tool_from_base_model(
     structured_model: Type[BaseModel],
diff --git a/tests/toolkit_basic_test.py b/tests/toolkit_basic_test.py
index ea079e8bb4..4028632b8b 100644
--- a/tests/toolkit_basic_test.py
+++ b/tests/toolkit_basic_test.py
@@ -472,12 +472,10 @@ def func_with_nested_model(a: MyBaseModel2) -> ToolResponse:
                                     "properties": {
                                         "c": {
                                             "description": "Field c",
-                                            "title": "C",
                                             "type": "integer",
                                         },
                                     },
                                     "required": ["c"],
-                                    "title": "MyBaseModel1",
                                     "type": "object",
                                 },
                                 "MyBaseModel2": {
@@ -490,12 +488,10 @@ def func_with_nested_model(a: MyBaseModel2) -> ToolResponse:
                                             "items": {
                                                 "$ref": "#/$defs/MyBaseModel1",
                                             },
-                                            "title": "B",
                                             "type": "array",
                                         },
                                     },
                                     "required": ["b"],
-                                    "title": "MyBaseModel2",
                                     "type": "object",
                                 },
                             },