.Net: Bug: .NET - Structured Output ResponseFormat schema incorrect for arrays of repeated types --- Invalid schema for response_format - reference can only point to definitions defined at the top level of the schema.

[AaronMacF]

Describe the bug
When using ResponseFormat = typeof(MyClass), the schema is incorrectly generated when two array properties use the same object type, leading to the following error:

{
  "error": {
    "message": "Invalid schema for response_format 'MyClass': In context=('properties', 'PropertyB', 'items'), reference can only point to definitions defined at the top level of the schema.",
    "type": "invalid_request_error",
    "param": "response_format",
    "code": null
  }
}

To Reproduce
Steps to reproduce the behavior:

See this MRE:

Program.cs

OpenAIPromptExecutionSettings executionSettings = new() { ResponseFormat = typeof(MyClass) };
 KernelArguments kernelArgs = new(executionSettings);
await kernel.InvokeAsync("PluginName", "FunctionName", kernelArgs);

MyClass.cs

public class MyClass
{
  public SubClass[] PropertyA { get; set; }
  public SubClass[] PropertyB { get; set; }
}

SubClass.cs

public class SubClass
{
  public string Property1 { get; set; }
  public int Property2 { get; set; }
}

Invalid generated schema:

{
  "response_format": {
    "json_schema": {
      "name": "MyClass",
      "schema": {
        "type": "object",
        "properties": {
          "PropertyA": {
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "Property1": { "type": "string" },
                "Property2": { "type": "integer" }
              },
              "additionalProperties": false,
              "required": ["Property1", "Property2"]
            }
          },
          "PropertyB": {
            "type": "array",
            "items": { "$ref": "#/properties/PropertyA/items" }
          }
        },
        "additionalProperties": false,
        "required": ["PropertyA", "PropertyB"]
      },
      "strict": true
    },
    "type": "json_schema"
  }
}

Expected valid schema

{
  "response_format": {
    "json_schema": {
      "name": "MyClass",
      "schema": {
        "type": "object",
        "properties": {
          "PropertyA": {
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "Property1": { "type": "string" },
                "Property2": { "type": "integer" }
              },
              "additionalProperties": false,
              "required": ["Property1", "Property2"]
            }
          },
          "PropertyB": {
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "Property1": { "type": "string" },
                "Property2": { "type": "integer" }
              },
              "additionalProperties": false,
              "required": ["Property1", "Property2"]
            }
          }
        },
        "additionalProperties": false,
        "required": ["PropertyA", "PropertyB"]
      },
      "strict": true
    },
    "type": "json_schema"
  }
}

Expected behavior
The generated schema is valid, and PropertyB doesn't use a reference to PropertyA

Platform

• Language: C#
• Source: Semantic Kernel version 1.33.0