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Official agent skill

Create Custom Agent

by dotnet in dotnet/skills

Creates VS Code custom agent files (.agent.md) for specialized AI personas with tools, instructions, and handoffs.

OfficialMITAuto-check passedAgent Workflows

Install Create Custom Agent

skills CLI
$ npx skills add dotnet/skills --skill create-custom-agent -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install dotnet/skills create-custom-agent --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/dotnet/skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/create-custom-agent .claude/skills/create-custom-agent && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
create-custom-agent
GitHub stars
5.6k
Used in
2 other repos
Token cost
~1.9k tokens
SKILL.md length
563 words
Files
1
Skills in repo
91
Repo updated
First seen
Licence
MIT

At a glance

Creates VS Code custom agent files (.agent.md) for specialized AI personas with tools, instructions, and handoffs.

  • Works in 6 steps: Create the agent file → Add YAML frontmatter → Configure tools → …
  • Scaffolding new custom agents
  • SKILL.md covers When to Use, When Not to Use, Inputs and Workflow, plus 5 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Create Custom Agent is an agent skill from dotnet/skills, published by the product's own GitHub organization. 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.

Its SKILL.md is about 1.9k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Agent Workflows, covering Project scaffolding and Multi-agent orchestration. It works with Visual Studio Code. The repository describes itself as: Repository for skills to assist AI coding agents with .NET and C. The licence is MIT.

When your agent uses it

  • Scaffolding new custom agents
  • Configuring agent workflows
  • Setting up agent-to-agent handoffs

Example prompts

  • “Use the create-custom-agent skill to create VS Code custom agent files (.agent.md) for specialized AI personas with tools, instructions, and handoffs”
  • “/create-custom-agent”

Workflow steps

6 steps, taken from the step headings in SKILL.md.

  1. Create the agent file
  2. Add YAML frontmatter
  3. Configure tools
  4. Add handoffs (optional)
  5. Write agent instructions (body)
  6. Validate the agent

What it can do on your machine

Read from SKILL.md and the folder at commit 8d670fa. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are markdown and yaml).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • code.visualstudio.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Create Custom Agent loads about 1.9k tokens when it runs. Until then it costs about 61 tokens; SKILL.md has 563 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~61
When it runs · the whole SKILL.md, loaded when a task matches
~1.9k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from dotnet/skills at commit 8d670fa, republished under its MIT licence (© dotnet). 563 words, ~1,900 tokens.

Download SKILL.mdSave it as .claude/skills/create-custom-agent/SKILL.md (or your agent's skills folder).
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

InputRequiredDescription
Agent nameYesDescriptive name for the agent (e.g., planner, code-reviewer)
DescriptionYesBrief description shown as placeholder text in chat
Purpose/PersonaYesWhat role the agent plays and how it should behave
ToolsRecommendedList of tools or tool sets the agent can use
HandoffsOptionalNext-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:

yaml
---
name: <agent-name>
description: <brief description for chat placeholder>
tools:
  - <tool-name>
  - <tool-set-name>
---
Available frontmatter fields:
FieldRequiredDescription
nameNoDisplay name (defaults to filename)
descriptionYesPlaceholder text shown in chat input
argument-hintNoHint text guiding user interaction
toolsNoList of available tools/tool sets
agentsNoList of allowed subagents (* for all, [] for none)
modelNoAI model name or prioritized array of models
handoffsNoList of next-step agent transitions
user-invokableNoShow in agents dropdown (default: true)
disable-model-invocationNoPrevent subagent invocation (default: false)
targetNoTarget environment: vscode or github-copilot
mcp-serversNoMCP server configs for GitHub Copilot target
Step 3: Configure tools

Specify which tools the agent can use:

yaml
tools:
  - search              # Built-in tool
  - fetch               # Built-in tool
  - codebase            # Tool set
  - myServer/*          # All tools from MCP server

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:

yaml
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 user
  • agent: Target agent identifier
  • prompt: Pre-filled prompt for target agent
  • send: Auto-submit prompt (default: false)
  • model: Optional model override for handoff
Show full SKILL.md (213 more words)Show less
Step 5: Write agent instructions (body)

Add the agent's behavior instructions in Markdown:

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:

  1. Open Command Palette (Ctrl+Shift+P)
  2. Run "Chat: New Custom Agent" or check agents dropdown
  3. Use "Diagnostics" view (right-click in Chat view) to check for errors

Template

markdown
---
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>
- <Guideline 2>
- <Guideline 3>

## Workflow

1. <Step 1>
2. <Step 2>
3. <Step 3>

## Constraints

- <Constraint 1>
- <Constraint 2>

Example Agents

Planning Agent
markdown
---
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
markdown
---
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

  • File has .agent.md extension
  • File is in agents/ directory
  • YAML frontmatter is valid (proper indentation, no syntax errors)
  • Description is non-empty and descriptive
  • Tools list contains only available tools
  • Handoff agent names match existing agents
  • Instructions are clear and actionable
  • Agent appears in agents dropdown

Common Pitfalls

PitfallSolution
Agent not appearing in dropdownCheck file is in agents/ directory with .agent.md extension
YAML syntax errorsValidate frontmatter indentation and quoting
Tools not workingVerify tool names exist; unavailable tools are ignored
Handoffs not showingTarget agent must exist; check agent identifier
Instructions too vagueBe specific about role, constraints, and workflow
Agent invoked as subagent unexpectedlySet disable-model-invocation: true
Want agent only as subagentSet user-invokable: false

References

© dotnet, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/create-custom-agent of dotnet/skills.

Open the folder on GitHubat commit 8d670fa

Used in 2 other repositories

We found 3 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 2 other GitHub owners. This page covers the copy in dotnet/skills, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Create Custom Agent next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Create Custom Agent compared with similar skills
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Create Custom Agent this skilldotnet/skills5.6k2 repos~1.9kAutomated safety check: PassMIT
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Configure Multiagentnetwaif/multi-agent-starter106—~629Automated safety check: PassMIT
Marm InitLyellr88/marm-memory419—~7.5kAutomated safety check: NotesApache-2.0
Omnigent Agent Builderomnigent-ai/omnigent11k—~2.1kAutomated safety check: PassApache-2.0
UI Widget Developermicrosoft/work-iq1k—~6.1kAutomated safety check: NotesCustom licence

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Works with

Categories

Questions about Create Custom Agent

What does Create Custom Agent do?

Creates VS Code custom agent files (.agent.md) for specialized AI personas with tools, instructions, and handoffs. Create Custom Agent is an agent skill from dotnet/skills, published by the product's own GitHub organization.md) for specialized AI personas with tools, instructions, and handoffs.

When should I use Create Custom Agent?

Create Custom Agent fits situations like: scaffolding new custom agents; configuring agent workflows; setting up agent-to-agent handoffs.

How do I install Create Custom Agent in Claude Code?

Run `npx skills add dotnet/skills --skill create-custom-agent -a claude-code`. Or copy the skill folder (.agents/skills/create-custom-agent in dotnet/skills) into .claude/skills/create-custom-agent in your project. Claude Code loads it when a task matches its description.

How do I install Create Custom Agent in Codex?

Run `npx skills add dotnet/skills --skill create-custom-agent -a codex`. Or copy the skill folder (.agents/skills/create-custom-agent in dotnet/skills) into .agents/skills/create-custom-agent in your project. Codex loads it when a task matches its description.

Can I use Create Custom Agent in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add dotnet/skills --skill create-custom-agent -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/create-custom-agent, .gemini/skills/create-custom-agent, .github/skills/create-custom-agent and .opencode/skills/create-custom-agent in your project.

What does Create Custom Agent need to run?

SKILL.md names no scripts, command-line tools or credentials: Create Custom Agent is instructions for the agent only.

Does Create Custom Agent access the network?

SKILL.md names 1 domain. As links in the text: code.visualstudio.com. This is read from the text; nothing was executed.

Is Create Custom Agent safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Create Custom Agent use?

Create Custom Agent is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Create Custom Agent use?

About 1.9k tokens (SKILL.md is roughly 7.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Create Custom Agent?

Skills that share tags, products or a category with Create Custom Agent: Team Agent Pipeline (zereight/gitlab-mcp, 2k stars), Configure Multiagent (netwaif/multi-agent-starter, 106 stars), Marm Init (Lyellr88/marm-memory, 419 stars) and Omnigent Agent Builder (omnigent-ai/omnigent, 11k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Create Custom Agent?

dotnet (a GitHub organization, an official publisher) maintains it in dotnet/skills, which has 5,568 GitHub stars. The repository holds 91 skills in this directory. The repository was last updated on October 7, 2026.

Source: dotnet/skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.