Custom Slash Commands for GitHub Copilot

Table of Contents

Custom Slash Commands for GitHub Copilot

You can create custom slash commands for GitHub Copilot.

I analyzed how spec-kit implements custom slash commands by examining the workspace structure and configuration files.

How to Create Custom Slash Commands for GitHub Copilot

Based on the spec-kit implementation, here’s how custom slash commands work:

Core Architecture

Custom slash commands consist of two types of files:

Prompt files (.github/prompts/*.prompt.md) - Simple triggers
Agent files (.github/agents/*.agent.md) - Full implementation logic

File Structure

.github/
├── prompts/
│   └── speckit.specify.prompt.md    # Simple pointer to agent
└── agents/
    └── speckit.specify.agent.md     # Full command logic

1. Prompt Files (.prompt.md)

These are minimal trigger files that reference the agent:

---
agent: speckit.specify
---

That’s it! The prompt file just tells Copilot which agent to invoke.

2. Agent Files (.agent.md)

These contain the actual command implementation with a frontmatter and instructions:

---
description: Brief description of what this command does
handoffs:
  - label: Next Command Label
    agent: speckit.nextcommand
    prompt: Suggested user prompt
    send: true # Optional: auto-send
---

## User Input

```text
$ARGUMENTS
```

Outline

[Your command’s detailed instructions…]

[Additional sections as needed]


**Key elements:**
- **description**: What the command does
- **handoffs**: Related commands to suggest next
- **$ARGUMENTS**: Captures text after the slash command
- **Instructions**: Detailed workflow for Copilot to follow

### 3. VS Code Settings Registration

Enable your commands in [.vscode/settings.json](.vscode/settings.json):

```json
{
    "chat.promptFilesRecommendations": {
        "speckit.specify": true,
        "speckit.plan": true,
        "yourname.mycommand": true
    }
}

Naming Convention

File names: namespace.commandname.{agent|prompt}.md
Example: speckit.specify.agent.md creates /speckit.specify command
The namespace (e.g., speckit) groups related commands

Creating Your Own Command - Example

Create .github/prompts/mykit.review.prompt.md:

---
agent: mykit.review
---

Create .github/agents/mykit.review.agent.md:

---
description: Review code for quality and best practices
handoffs:
  - label: Fix Issues
    agent: mykit.fix
    prompt: Fix the identified issues
---

## User Input

```text
$ARGUMENTS
```

Outline

Analyze the current file or selected code
Check for:
- Code quality issues
- Best practice violations
- Security concerns
Generate a detailed report
Suggest improvements


3. Add to [.vscode/settings.json](.vscode/settings.json):
```json
{
    "chat.promptFilesRecommendations": {
        "mykit.review": true
    }
}

Advanced Features

Scripts: Commands can invoke bash/PowerShell scripts in .specify/scripts/
Templates: Store reusable content in .specify/templates/
Auto-approval: Configure trusted scripts in settings for auto-execution
Handoffs: Chain commands together with suggested follow-ups

The system is very flexible - you can create simple commands with basic instructions or complex workflows with multiple phases, script execution, and file generation!### Advanced Features

Scripts: Commands can invoke bash/PowerShell scripts in .specify/scripts/
Templates: Store reusable content in .specify/templates/
Auto-approval: Configure trusted scripts in settings for auto-execution
Handoffs: Chain commands together with suggested follow-ups

The system is very flexible - you can create simple commands with basic instructions or complex workflows with multiple phases, script execution, and file generation!

.vscode.settings.json

It’s not required, but it’s highly recommended for better user experience.

How commands work:

Without settings.json:

Commands still work if you type them manually (e.g., /speckit.specify)
Copilot finds them from .github/prompts/*.prompt.md files
No autocomplete suggestions when typing /

With chat.promptFilesRecommendations:

✅ Commands appear in autocomplete dropdown
✅ Users discover available commands easily
✅ Shows command descriptions
✅ Better IDE integration

Best practice:

{
  "chat.promptFilesRecommendations": {
    "mykit.review": true,
    "mykit.fix": true,
    "mykit.test": true
  }
}

When to use settings.json:

Commands you want users to easily discover
Team/project-specific workflows
Commands used frequently

When to skip:

Experimental/internal commands
Commands you want to keep “hidden”
Single-user temporary commands

Alternative locations:

You can also define this in:

User settings (settings.json) - personal commands
Workspace settings (settings.json) - team/project commands ← Recommended for shared projects