.NET Agent Skills marketplace example

# How to use the dotnet/skills marketplace with Copilot

The dotnet/skills repository is the .NET team's curated marketplace of agent plugins, skills, and custom agents for coding agents. It gives you a concrete example of the newer marketplace model: add a trusted catalog, install a plugin such as dotnet or dotnet-diag, restart Copilot, then use the loaded skills and agents in a real .NET workflow.

What the marketplace is for

This marketplace lets .NET developers add focused capabilities for diagnostics, ASP.NET Core, testing, upgrades, NuGet, templates, AI, and other common .NET tasks.

Add marketplace Install plugin Load skills Use in workflow
Why this is a strong demo
The repository already publishes a named marketplace, dotnet-agent-skills, with install instructions for Copilot CLI. That makes it much easier to show an end-to-end story than a generic "plugin marketplace" mockup.

## How a user should use the marketplace

The flow for dotnet/skills is simple: add the marketplace, install a plugin, restart Copilot, then use the new skills or agents on a real .NET task.

1

### Add the marketplace

Register the .NET team's marketplace with /plugin marketplace add dotnet/skills.

2

### Pick a plugin

Choose a plugin that matches the job, such as dotnet, dotnet-diag, or dotnet-aspnet.

3

### Install it

Install from the marketplace with /plugin install <plugin>@dotnet-agent-skills.

4

### Restart Copilot

Restart so the newly installed plugin can load its skills, language server, or custom agents.

5

### Use the new capabilities

Run /skills or /agents, then ask Copilot to apply the installed plugin to your current .NET problem.

## Examples from the dotnet/skills marketplace

These examples come directly from the plugins published in the dotnet/skills repository.

### dotnet

Core .NET development

Common everyday C# and .NET skills, plus a C# language server integration for .cs files.

- Core .NET coding tasks
- C# language-aware help
- Useful default plugin for most .NET repos

### dotnet-diag

Diagnostics and performance

Skills for .NET performance investigations, debugging, and incident analysis.

- Analyze .NET performance problems
- Collect traces and dumps
- Use the optimizing-dotnet-performance agent

### dotnet-aspnet

ASP.NET Core

ASP.NET Core web development skills for middleware, endpoints, real-time communication, and API patterns.

- Design and troubleshoot endpoints
- Work through middleware behavior
- Get help with common API patterns

### dotnet-test

Testing

Skills for running, diagnosing, and migrating .NET tests across platforms and test frameworks.

- Run and filter tests faster
- Diagnose broken test runs
- Handle MSTest workflows

### dotnet-upgrade

Modernization

Guidance for migrating and upgrading .NET projects across framework versions, language features, and compatibility targets.

- Plan framework upgrades
- Modernize language features
- Reduce upgrade risk

### dotnet-ai

AI and ML

AI and ML skills for .NET, including LLM integration, RAG pipelines, MCP, and classic ML with ML.NET.

- Choose the right AI approach
- Design agentic workflows in .NET
- Connect AI ideas to shipping code

## Commands to add dotnet/skills and install a plugin

These are the concrete commands published in the repository README for Copilot CLI.

1. Launch Copilot CLI
copilot
2. Add the marketplace
/plugin marketplace add dotnet/skills

This registers the dotnet-agent-skills marketplace from the .NET team.

3. Install a plugin from the marketplace
/plugin install dotnet-diag@dotnet-agent-skills

Swap in other plugins such as dotnet, dotnet-aspnet, or dotnet-test.

4. Restart Copilot
exit copilot

Restarting loads the newly installed plugin into the session.

5. Show available skills
/skills

Use this to prove the plugin loaded and to show which skills are now available.

6. Show available custom agents
/agents

This is especially useful after installing dotnet-diag, which ships a performance-focused agent.

7. Use the installed plugin in a real prompt
Investigate why this .NET service is slow under load. Use the installed diagnostics capabilities to suggest the next trace or dump command, explain what data to collect, and point out the most likely hot paths to inspect first.

After installation, the goal is not to call the marketplace again; it is to use the newly loaded skills in normal Copilot work.

8. Update the plugin later
/plugin update dotnet-diag@dotnet-agent-skills

The same naming pattern works for updates: <plugin>@dotnet-agent-skills.

## Design principles for a new marketplace

The .NET marketplace is a good reference because it is curated around real developer tasks instead of generic app categories.

Curate by developer workflow

Each plugin maps to a recognizable .NET need such as diagnostics, ASP.NET Core, testing, upgrades, or AI integration.

Make installation obvious

The add-marketplace and install commands are short, repeatable, and easy to demo live.

Connect installation to usage

A good marketplace example does not stop at install time; it immediately shows the new skill or agent solving a real engineering task.

## Worked example: install dotnet-diag and use it

Here is a concrete example you can demo live. The developer adds the marketplace, installs dotnet-diag, and then uses the loaded diagnostics skills to investigate a performance problem in a .NET service.

### User journey

- Run /plugin marketplace add dotnet/skills.
- Install /plugin install dotnet-diag@dotnet-agent-skills.
- Restart Copilot, then inspect /skills and /agents.
- Ask Copilot to use those diagnostics capabilities against the current codebase or incident.

Example prompt to Copilot: "This ASP.NET Core service gets slow after a few minutes of load. Use the installed .NET diagnostics capabilities to explain whether I should start with a trace, dump, or benchmark, tell me the next command to run, and outline how you would narrow down the hot path."

### Expected result

- Copilot uses the plugin's diagnostics knowledge to recommend the right investigation path.
- It suggests concrete next commands such as trace or dump collection instead of generic advice.
- The developer gets an agent-ready .NET workflow without hunting for separate troubleshooting docs.

Why dotnet/skills works well as a marketplace demo

It has a real marketplace name, concrete install commands, multiple focused plugins, and at least one custom agent. That gives you both the "how to add it" story and the "what do I do with it next" story on one page.

Simple rule of thumb

Add dotnet/skills, install the plugin that matches the task, restart, then use /skills, /agents, and a focused prompt to show the value.