From 91a434441f4d4eaf715d7cbeeeb5c525b25d4fdb Mon Sep 17 00:00:00 2001
From: Gautam Datla <gautamdsrc@gmail.com>
Date: Tue, 10 Mar 2026 03:23:44 -0400
Subject: [PATCH] fix: populate required for Pydantic BaseModel parameter
 schemas

---
 .../tools/_function_parameter_parse_util.py   |  7 +++
 .../tools/test_build_function_declaration.py  | 59 +++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/src/google/adk/tools/_function_parameter_parse_util.py b/src/google/adk/tools/_function_parameter_parse_util.py
index 1b9559b29c..03c8ff9d0c 100644
--- a/src/google/adk/tools/_function_parameter_parse_util.py
+++ b/src/google/adk/tools/_function_parameter_parse_util.py
@@ -399,6 +399,13 @@ def _parse_schema_from_parameter(
           ),
           func_name,
       )
+    required_fields = [
+        field_name
+        for field_name, field_info in param.annotation.model_fields.items()
+        if field_info.is_required()
+    ]
+    if required_fields:
+      schema.required = required_fields
     _raise_if_schema_unsupported(variant, schema)
     return schema
   if inspect.isclass(param.annotation) and issubclass(
diff --git a/tests/unittests/tools/test_build_function_declaration.py b/tests/unittests/tools/test_build_function_declaration.py
index 1c9bf245f1..608f06cb13 100644
--- a/tests/unittests/tools/test_build_function_declaration.py
+++ b/tests/unittests/tools/test_build_function_declaration.py
@@ -124,6 +124,65 @@ def simple_function(input: CustomInput) -> str:
   )
 
 
+def test_basemodel_required_fields():
+  class SearchRequest(BaseModel):
+    query: str
+    max_results: int
+    filter: str = ''
+
+  def search(request: SearchRequest) -> list:
+    return []
+
+  function_decl = _automatic_function_calling_util.build_function_declaration(
+      func=search
+  )
+
+  inner = function_decl.parameters.properties['request']
+  assert set(inner.required) == {'query', 'max_results'}
+  assert 'filter' not in (inner.required or [])
+
+
+def test_basemodel_all_optional_fields_no_required():
+  class Config(BaseModel):
+    timeout: int = 30
+    retries: int = 3
+
+  def run(config: Config) -> str:
+    return ''
+
+  function_decl = _automatic_function_calling_util.build_function_declaration(
+      func=run
+  )
+
+  inner = function_decl.parameters.properties['config']
+  assert not inner.required
+
+
+def test_nested_basemodel_required_fields():
+  class Inner(BaseModel):
+    x: int
+    y: int = 0
+
+  class Outer(BaseModel):
+    inner: Inner
+    label: str = ''
+
+  def process(data: Outer) -> str:
+    return ''
+
+  function_decl = _automatic_function_calling_util.build_function_declaration(
+      func=process
+  )
+
+  outer = function_decl.parameters.properties['data']
+  assert set(outer.required) == {'inner'}
+  assert 'label' not in (outer.required or [])
+
+  inner = outer.properties['inner']
+  assert set(inner.required) == {'x'}
+  assert 'y' not in (inner.required or [])
+
+
 def test_toolcontext_ignored():
   def simple_function(input_str: str, tool_context: ToolContext) -> str:
     return {'result': input_str}