Include default values in tool arguments JSON schema (#2418)

Author: DouweM

pydantic_ai_slim/pydantic_ai/_function_schema.py

@@ -154,17 +154,21 @@ def function_schema(  # noqa: C901
             if p.kind == Parameter.VAR_POSITIONAL:
                 annotation = list[annotation]
 
-            # FieldInfo.from_annotation expects a type, `annotation` is Any
+            required = p.default is Parameter.empty
+            # FieldInfo.from_annotated_attribute expects a type, `annotation` is Any
             annotation = cast(type[Any], annotation)
-            field_info = FieldInfo.from_annotation(annotation)
+            if required:
+                field_info = FieldInfo.from_annotation(annotation)
+            else:
+                field_info = FieldInfo.from_annotated_attribute(annotation, p.default)
             if field_info.description is None:
                 field_info.description = field_descriptions.get(field_name)
 
             fields[field_name] = td_schema = gen_schema._generate_td_field_schema(  # pyright: ignore[reportPrivateUsage]
                 field_name,
                 field_info,
                 decorators,
-                required=p.default is Parameter.empty,
+                required=required,
             )
             # noinspection PyTypeChecker
             td_schema.setdefault('metadata', {})['is_model_like'] = is_model_like(annotation)

tests/models/test_openai.py

@@ -1144,17 +1144,16 @@ def tool_with_tuples(x: tuple[int], y: tuple[str] = ('abc',)) -> str:
             snapshot(None),
         ),
         (
-            strict_compatible_tool,
+            tool_with_default,
             None,
             snapshot(
                 {
                     'additionalProperties': False,
-                    'properties': {'x': {'type': 'integer'}},
-                    'required': ['x'],
+                    'properties': {'x': {'default': 1, 'type': 'integer'}},
                     'type': 'object',
                 }
             ),
-            snapshot(True),
+            snapshot(None),
         ),
         (
             tool_with_recursion,
@@ -1413,6 +1412,7 @@ def tool_with_tuples(x: tuple[int], y: tuple[str] = ('abc',)) -> str:
                     'properties': {
                         'x': {'maxItems': 1, 'minItems': 1, 'prefixItems': [{'type': 'integer'}], 'type': 'array'},
                         'y': {
+                            'default': ['abc'],
                             'maxItems': 1,
                             'minItems': 1,
                             'prefixItems': [{'type': 'string'}],

tests/test_tools.py

@@ -932,7 +932,7 @@ def my_tool_plain(*, a: int = 1, b: int) -> int:
                 'outer_typed_dict_key': None,
                 'parameters_json_schema': {
                     'additionalProperties': False,
-                    'properties': {'a': {'type': 'integer'}, 'b': {'type': 'integer'}},
+                    'properties': {'a': {'type': 'integer'}, 'b': {'default': 1, 'type': 'integer'}},
                     'required': ['a'],
                     'type': 'object',
                 },
@@ -945,7 +945,7 @@ def my_tool_plain(*, a: int = 1, b: int) -> int:
                 'outer_typed_dict_key': None,
                 'parameters_json_schema': {
                     'additionalProperties': False,
-                    'properties': {'a': {'type': 'integer'}, 'b': {'type': 'integer'}},
+                    'properties': {'a': {'default': 1, 'type': 'integer'}, 'b': {'type': 'integer'}},
                     'required': ['b'],
                     'type': 'object',
                 },
@@ -1031,7 +1031,7 @@ def my_tool(x: Annotated[Union[str, None], WithJsonSchema({'type': 'string'})] =
                 'name': 'my_tool_1',
                 'outer_typed_dict_key': None,
                 'parameters_json_schema': {
-                    'properties': {'x': {'type': 'string'}},
+                    'properties': {'x': {'default': None, 'type': 'string'}},
                     'type': 'object',
                 },
                 'strict': None,
@@ -1042,7 +1042,7 @@ def my_tool(x: Annotated[Union[str, None], WithJsonSchema({'type': 'string'})] =
                 'name': 'my_tool_2',
                 'outer_typed_dict_key': None,
                 'parameters_json_schema': {
-                    'properties': {'x': {'type': 'string', 'title': 'X title'}},
+                    'properties': {'x': {'default': None, 'type': 'string', 'title': 'X title'}},
                     'type': 'object',
                 },
                 'strict': None,