Create a Custom Agent

## Overview

Custom agents let you create specialized Copilot personas with specific instructions, tools, and behaviors. This recipe shows you how to create one from scratch.

## Steps

### 1. Create the agent file

Create `.github/agents/my-agent.agent.md`:

```markdown
---
name: my-agent
description: "Helps with database migrations and schema design"
tools:
  - name: github
  - name: postgres
---

You are an expert database engineer. When asked about schema design:
- Always suggest migrations, never direct ALTER TABLE
- Use snake_case for column names
- Add created_at and updated_at to every table
- Prefer UUID over auto-increment for primary keys
```

### 2. Add MCP server connections (optional)

Reference MCP servers in the `tools` frontmatter:

```yaml
tools:
  - name: github
  - name: postgres
    config:
      connectionString: "${DATABASE_URL}"
```

### 3. Test the agent

1. Open Copilot Chat in VS Code
2. Type `@my-agent` to invoke it
3. Ask: "Design a schema for a blog with posts and comments"

## Best Practices

- Keep the system prompt focused on one domain
- List specific do's and don'ts
- Reference MCP servers only when the agent needs external data
- Test with real scenarios before sharing