Python: fix build_model_schema putting pydantic constraint objects into field descriptions

python/semantic_kernel/schema/kernel_json_schema_builder.py

@@ -91,9 +91,10 @@ def build_model_schema(
                 field_info = model.model_fields[field_name]
                 if isinstance(field_info.metadata, dict):
                     field_description = field_info.metadata.get("description")
-                elif isinstance(field_info.metadata, list) and field_info.metadata:
-                    field_description = field_info.metadata[0]
                 elif hasattr(field_info, "description"):
+                    # Pydantic v2 keeps constraints (Ge, Le, ...) in field_info.metadata,
+                    # which is a list of constraint objects and not a description,
+                    # so the description must come from field_info.description instead.
                     field_description = field_info.description
             if not cls._is_optional(field_type):
                 required.append(field_name)

python/tests/unit/schema/test_schema_builder.py

@@ -6,6 +6,7 @@
 from unittest.mock import Mock
 
 import pytest
+from pydantic import Field
 
 from semantic_kernel.connectors.utils.structured_output_schema import generate_structured_output_response_format_schema
 from semantic_kernel.kernel_pydantic import KernelBaseModel
@@ -455,3 +456,16 @@ def test_build_schema_with_nonpydantic_structured_output():
     }
 
     assert structured_output_schema == expected_schema
+
+
+class ConstrainedParams(KernelBaseModel):
+    top_p: float = Field(default=0.9, ge=0.0, le=1.0, description="nucleus sampling")
+
+
+def test_build_model_schema_with_field_constraints_keeps_description():
+    # Regression test for https://github.com/microsoft/semantic-kernel/issues/14443:
+    # pydantic constraint objects (Ge, Le, ...) live in FieldInfo.metadata and
+    # must not end up in the field description.
+    schema = KernelJsonSchemaBuilder.build_model_schema(ConstrainedParams)
+    assert schema["properties"]["top_p"]["description"] == "nucleus sampling"
+    json.dumps(schema)  # the schema must be JSON serializable