Property ordering and supported types for structured JSON output with Gemini

[SeyitcanOz]

JSON Property Ordering and Dictionary Support Issues with Gemini APIs

Issue Summary

I'm experiencing two related issues when working with structured outputs and the Gemini API integration:

1. JSON Property Ordering: JsonPropertyOrder attributes are not being respected in the output
2. Dictionary Support: Using Dictionary<TKey, TValue> properties results in "bad request" errors from Gemini API

Environment

• Semantic Kernel Version: 1.57
• Target API: Google Gemini
• .NET Version: .NET 9
• Serialization Library: System.Text.Json

Code Example

Here's my model class with JsonPropertyOrder attributes:

public class StructuralCommandParseResult
{
    [Description("Whether the user input contains sufficient information to proceed with the requested operations")]
    [Required]
    [JsonPropertyOrder(1)]
    public bool IsSufficient { get; set; }

    [Description("Confidence level in the analysis accuracy (0.0 = no confidence, 1.0 = complete confidence)")]
    [Required]
    [Range(0.0, 1.0)]
    [JsonPropertyOrder(2)]
    public double Confidence { get; set; }

    [Description("List of operations identified in the user request")]
    [Required]
    [MinLength(1)]
    [JsonPropertyOrder(3)]
    public List<OperationType> Operations { get; set; } = new List<OperationType>();

    [Description("Detailed analysis of each operation found in the request")]
    [Required]
    [JsonPropertyOrder(4)]
    public List<OperationDetail> Details { get; set; } = new List<OperationDetail>();

    [Description("Helpful suggestions for the user to complete incomplete requests or improve their commands")]
    [Required]
    [JsonPropertyOrder(5)]
    public List<string> Suggestions { get; set; } = new List<string>();

    [Description("Status messages, warnings, and errors about the parsed command")]
    [Required]
    [JsonPropertyOrder(6)]
    public List<ParseMessage> Messages { get; set; } = new List<ParseMessage>();
}

Questions

1. JSON Property Ordering

The JsonPropertyOrder attributes don't seem to affect the actual JSON output order when using Gemini APIs. The properties appear in a different order than specified.

• Is JsonPropertyOrder supported with the current Gemini API integration?
• Are there any specific serialization settings required?
• Is there an alternative approach to ensure consistent property ordering?

2. Dictionary Support

When I include Dictionary<string, object> or similar dictionary properties in my response models, I consistently receive "bad request" errors from the Gemini API.

• Are dictionaries officially supported in structured outputs for Gemini APIs?
• If not, what's the recommended alternative for key-value pair data?
• Are there any workarounds or specific patterns that work?

Expected Behavior

• JSON properties should appear in the order specified by JsonPropertyOrder
• Dictionary properties should be serialized and accepted by the Gemini API

Actual Behavior

• Properties appear in undefined/alphabetical order
• Dictionary properties cause "bad request" errors

Additional Context

This affects the reliability of my structured outputs, especially when property order matters for downstream processing or when I need flexible key-value data structures.

Any guidance on these issues would be greatly appreciated!