What Can the dotnet11 Plugin Do for .NET 11 Development?

The dotnet11 plugin provides AI agents with structured skills to explore System.Text.Json APIs, generate serialization code, diagnose migration issues, and validate .NET 11 JSON features through the system-text-json-net11 skill.

The dotnet11 plugin in the dotnet/skills repository provides AI agents with specialized capabilities for .NET 11 development. It ships a focused system-text-json-net11 skill that exposes the latest System.Text.Json APIs while following the agentskills.io specification for seamless integration with Copilot, Claude, and Codex.

Core Capabilities of the dotnet11 Plugin

The plugin targets .NET 11's newest APIs through four primary functions:

Explore the .NET 11 System.Text.Json API Surface

Agents can enumerate new types, members, and overloads introduced in .NET 11. The skill returns structured data including apiVersion, availableTypes, and specific member details like JsonSerializerOptions.DefaultBufferSize and ReferenceHandler properties.

Generate JSON Serialization Code

The skill produces production-ready C# code including JsonSerializerOptions configurations, custom converters, and attribute usage that leverage .NET 11 performance improvements. This includes specialized handling for new polymorphic scenarios.

Diagnose Migration Issues from .NET 10

When upgrading existing codebases, the plugin compares .NET 10 JSON implementations against .NET 11 requirements. It highlights breaking changes—such as default buffer size adjustments—and suggests automated refactorings.

Run Inline Validation

The plugin compiles and executes small code snippets exercising new APIs, returning compile-time and runtime diagnostics. This allows agents to verify API usage before generating final project code.

How to Invoke the dotnet11 Skill

The skill accepts JSON input through the dotnet11.system-text-json-net11 endpoint. Below are practical examples for common scenarios.

Query New System.Text.Json Members

{
  "skill": "dotnet11.system-text-json-net11",
  "input": {
    "action": "list-new-members",
    "target": "JsonSerializer"
  }
}

The response includes apiVersion, availableMembers, and sampleCode:

{
  "apiVersion": "11.0",
  "availableMembers": [
    "JsonSerializerOptions.DefaultBufferSize",
    "JsonSerializerOptions.ReferenceHandler",
    "JsonSerializerOptions.UnknownTypeHandling"
  ],
  "sampleCode": "var options = new JsonSerializerOptions { ReferenceHandler = ReferenceHandler.Preserve };"
}

Generate Custom Converters for Records

{
  "skill": "dotnet11.system-text-json-net11",
  "input": {
    "action": "generate-converter",
    "typeName": "MyRecord"
  }
}

This returns a complete converter implementation:

public class MyRecordConverter : JsonConverter<MyRecord>
{
    public override MyRecord Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        => JsonSerializer.Deserialize<MyRecord>(ref reader, options);

    public override void Write(Utf8JsonWriter writer, MyRecord value, JsonSerializerOptions options)
        => JsonSerializer.Serialize(writer, value, options);
}

Validate .NET 10 to .NET 11 Migrations

{
  "skill": "dotnet11.system-text-json-net11",
  "input": {
    "action": "compare-versions",
    "oldCode": "JsonSerializer.Serialize(obj, new JsonSerializerOptions());",
    "targetVersion": "11.0"
  }
}

The plugin identifies specific migration issues:

{
  "issues": [
    {
      "line": 1,
      "description": "DefaultBufferSize property now defaults to 16 KB; consider adjusting for large payloads."
    }
  ],
  "suggestedFix": "var opts = new JsonSerializerOptions { DefaultBufferSize = 32_768 };"
}

Plugin Architecture and Key Files

The dotnet11 plugin follows the standard .NET skills structure with specific metadata files enabling agent discovery.

Core Configuration Files

• plugins/dotnet11/plugin.json: Registers the plugin with the agentskills framework and declares compatibility with the skill-validator pipeline.
• plugins/dotnet11/.codex-plugin/plugin.json: Codex-specific manifest enabling installation via the Codex CLI.
• plugins/dotnet11/README.md: Overview documentation describing the plugin's purpose and installation requirements.

Skill Definition

The concrete implementation resides in plugins/dotnet11/skills/system-text-json-net11/SKILL.md. This document defines:

• Input/output schemas
• Action parameters (list-new-members, generate-converter, compare-versions)
• Response structures including recommendedConverters and validation diagnostics

Because the plugin installs alongside other .NET plugins (such as dotnet, dotnet-advanced, and dotnet-diag), it supports multi-step workflows like "upgrade a project to .NET 11 and then add JSON serialization."

Summary

• The dotnet11 plugin provides the system-text-json-net11 skill for .NET 11 development, exposing new JSON APIs through structured agent interactions.
• It supports four core operations: API exploration, code generation, migration diagnostics, and inline validation.
• Located in plugins/dotnet11/ within the dotnet/skills repository, it integrates with the agentskills.io ecosystem for Copilot, Claude, and Codex compatibility.
• Responses include structured JSON with apiVersion, availableTypes, recommendedConverters, and ready-to-use sampleCode.
• The plugin works alongside other .NET skills to enable complex agentic workflows targeting .NET 11 upgrades.

Frequently Asked Questions

What agents are compatible with the dotnet11 plugin?

The dotnet11 plugin adheres to the agentskills.io specification, making it compatible with GitHub Copilot, Anthropic's Claude, OpenAI's Codex, and any other agent framework that respects this standard. The plugin.json metadata ensures automatic discovery and validation by these systems.

How does the dotnet11 plugin handle breaking changes from .NET 10?

The plugin's compare-versions action analyzes existing .NET 10 JSON code against .NET 11 requirements, identifying specific breaking changes such as modified DefaultBufferSize defaults. It returns structured diagnostics with line numbers and suggested fixes to streamline migration.

Can the dotnet11 plugin generate production-ready code?

Yes. The generate-converter action produces complete C# implementations including proper JsonConverter<T> inheritance, Utf8JsonReader handling, and JsonSerializerOptions integration. The generated code leverages .NET 11 performance optimizations and handles new polymorphic serialization scenarios.

Where is the dotnet11 plugin installed in the dotnet/skills repository?

The plugin resides in the plugins/dotnet11/ directory, with its skill definition located at plugins/dotnet11/skills/system-text-json-net11/SKILL.md. Configuration files include plugins/dotnet11/plugin.json for general registration and plugins/dotnet11/.codex-plugin/plugin.json for Codex-specific installations.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}