| name | create-custom-agent |
| description | Creates VS Code custom agent files (.agent.md) for specialized AI personas with tools, instructions, and handoffs. Use when scaffolding new custom agents, configuring agent workflows, or setting up agent-to-agent handoffs. |
Create Custom Agent
This skill helps you create VS Code custom agent files that define specialized AI personas for development tasks. Custom agents configure which tools are available, provide specialized instructions, and can chain together via handoffs.
When to Use
- Creating a new custom agent from scratch
- Scaffolding an
.agent.md file with proper frontmatter
- Setting up agent-to-agent handoffs for multi-step workflows
- Configuring tool restrictions for specialized roles (planner, reviewer, etc.)
- Creating workspace-shared or user-profile agents
When Not to Use
- Creating instruction files (use
.instructions.md instead)
- Creating reusable prompts (use
.prompt.md instead)
- Modifying existing agents (edit the file directly)
Inputs
| Input | Required | Description |
|---|
| Agent name | Yes | Descriptive name for the agent (e.g., planner, code-reviewer) |
| Description | Yes | Brief description shown as placeholder text in chat |
| Purpose/Persona | Yes | What role the agent plays and how it should behave |
| Tools | Recommended | List of tools or tool sets the agent can use |
| Handoffs | Optional | Next-step agents to transition to after completing work |
Workflow
Step 1: Create the agent file
Create a file with .agent.md extension in the agents/ directory:
agents/<agent-name>.agent.md
Step 2: Add YAML frontmatter
Add the header with required and optional fields:
---
name: <agent-name>
description: <brief description for chat placeholder>
tools:
- <tool-name>
- <tool-set-name>
---
Available frontmatter fields:
| Field | Required | Description |
|---|
name | No | Display name (defaults to filename) |
description | Yes | Placeholder text shown in chat input |
argument-hint | No | Hint text guiding user interaction |
tools | No | List of available tools/tool sets |
agents | No | List of allowed subagents (* for all, [] for none) |
model | No | AI model name or prioritized array of models |
handoffs | No | List of next-step agent transitions |
user-invokable | No | Show in agents dropdown (default: true) |
disable-model-invocation | No | Prevent subagent invocation (default: false) |
target | No | Target environment: vscode or github-copilot |
mcp-servers | No | MCP server configs for GitHub Copilot target |
Step 3: Configure tools
Specify which tools the agent can use:
tools:
- search
- fetch
- codebase
- myServer/*
Common tool patterns:
- Read-only agents:
['search', 'fetch', 'codebase']
- Full editing agents:
['*'] or specific editing tools
- Specialized agents: Cherry-pick specific tools
Step 4: Add handoffs (optional)
Configure transitions to other agents:
handoffs:
- label: Start Implementation
agent: implementation
prompt: Implement the plan outlined above.
send: false
model: GPT-5.2 (copilot)
Handoff fields:
label: Button text displayed to useragent: Target agent identifierprompt: Pre-filled prompt for target agentsend: Auto-submit prompt (default: false)model: Optional model override for handoff
Step 5: Write agent instructions (body)
Add the agent's behavior instructions in Markdown:
You are a security-focused code reviewer. Your job is to:
1. Analyze code for security vulnerabilities
2. Check for common security anti-patterns
3. Suggest secure alternatives
## Guidelines
- Focus on OWASP Top 10 vulnerabilities
- Flag hardcoded secrets immediately
- Review authentication and authorization logic
## Reference other files
See [security guidelines](../security.md) for standards.
Tips for instructions:
- Use Markdown links to reference other files
- Reference tools with
#tool:<tool-name> syntax
- Be specific about agent behavior and constraints
Step 6: Validate the agent
Verify the agent loads correctly:
- Open Command Palette (Ctrl+Shift+P)
- Run "Chat: New Custom Agent" or check agents dropdown
- Use "Diagnostics" view (right-click in Chat view) to check for errors
Template
---
name: <agent-name>
description: <brief description for chat placeholder>
argument-hint: <optional hint for user input>
tools:
- <tool-1>
- <tool-2>
handoffs:
- label: <button-text>
agent: <target-agent>
prompt: <pre-filled-prompt>
send: false
---
# <Agent Title>
<One paragraph describing the agent's persona and purpose.>
## Role
<Describe the agent's specialized role and expertise.>
## Guidelines
- <Guideline 1>
-
Example Agents
Planning Agent
---
name: planner
description: Generate an implementation plan
tools:
- search
- fetch
- codebase
handoffs:
- label: Start Implementation
agent: implementation
prompt: Implement the plan above.
---
# Planning Agent
You are a solution architect. Generate detailed implementation plans.
## Guidelines
- Analyze requirements thoroughly before planning
- Break work into discrete, testable steps
- Identify dependencies and risks
- Do NOT make code changes
Code Review Agent
---
name: code-reviewer
description: Review code for quality and security issues
tools:
- search
- codebase
---
# Code Review Agent
You are a senior engineer performing code review.
## Focus Areas
- Security vulnerabilities
- Performance concerns
- Code maintainability
- Test coverage gaps
## Output Format
Provide findings as:
1. **Critical**: Must fix before merge
2. **Warning**: Should address
3. **Suggestion**: Nice to have
Validation Checklist
Common Pitfalls
| Pitfall | Solution |
|---|
| Agent not appearing in dropdown | Check file is in agents/ directory with .agent.md extension |
| YAML syntax errors | Validate frontmatter indentation and quoting |
| Tools not working | Verify tool names exist; unavailable tools are ignored |
| Handoffs not showing | Target agent must exist; check agent identifier |
| Instructions too vague | Be specific about role, constraints, and workflow |
| Agent invoked as subagent unexpectedly | Set disable-model-invocation: true |
| Want agent only as subagent | Set user-invokable: false |
References
