MCPInstall

agent-customization

by microsoft OfficialAI & Agents

WORKFLOW SKILL — Create, update, review, fix, or debug VS Code agent customization files (.instructions.md, .prompt.md, .agent.md, SKILL.md, copilot-instructions.md, AGENTS.md). USE FOR: saving coding preferences; troubleshooting why instructions/skills/agents are ignored or not invoked; configuring applyTo patterns; defining tool restrictions; creating custom agent modes or specialized workflows; packaging domain knowledge; fixing YAML frontmatter syntax. DO NOT USE FOR: general coding questions (use default agent); runtime debugging or error diagnosis; MCP server configuration (use MCP docs directly); VS Code extension development. INVOKES: file system tools (read/write customization files), ask-questions tool (interview user for requirements), subagents for codebase exploration. FOR SINGLE OPERATIONS: For quick YAML frontmatter fixes or creating a single file from a known pattern, edit the file directly — no skill needed.

Installs
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Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/microsoft/vscode-copilot-chat --skill agent-customization
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads agent-customization automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

Agent Customization

Decision Flow

PrimitiveWhen to Use
Workspace InstructionsAlways-on, applies everywhere in the project
File InstructionsExplicit via applyTo patterns, or on-demand via description
MCPIntegrates external systems, APIs, or data
HooksDeterministic shell commands at agent lifecycle points (block tools, auto-format, inject context)
Custom AgentsSubagents for context isolation, or multi-stage workflows with tool restrictions
PromptsSingle focused task with parameterized inputs
SkillsOn-demand workflow with bundled assets (scripts/templates)

Quick Reference

Consult the reference docs for templates, domain examples, advanced frontmatter options, asset organization, anti-patterns, and creation checklists. If the references are not enough, load the official documentation links for each primitive.

TypeFileLocationReference
Workspace Instructionscopilot-instructions.md, AGENTS.md.github/ or rootLink
File Instructions*.instructions.md.github/instructions/Link
Prompts*.prompt.md.github/prompts/Link
Hooks*.json.github/hooks/Link
Custom Agents*.agent.md.github/agents/Link
SkillsSKILL.md.github/skills/<name>/, .agents/skills/<name>/, .claude/skills/<name>/Link

User-level: {{VSCODE_USER_PROMPTS_FOLDER}}/ (*.prompt.md, *.instructions.md, *.agent.md; not skills) Customizations roam with user's settings sync

Creation Process

If you need to explore or validate patterns in the codebase, use a read-only subagent. If the ask-questions tool is available, use it to interview the user and clarify requirements.

Follow these steps when creating any customization file.

1. Determine Scope

Ask the user where they want the customization:

  • Workspace: For project-specific, team-shared customizations → .github/ folder
  • User profile: For personal, cross-workspace customizations → {{VSCODE_USER_PROMPTS_FOLDER}}/

2. Choose the Right Primitive

Use the Decision Flow above to select the appropriate file type based on the user's need.

3. Create the File

Create the file directly at the appropriate path:

  • Use the location tables in each reference file
  • Include required frontmatter as needed
  • Add the body content following the templates

4. Validate

After creating:

  • Confirm the file is in the correct location
  • Verify frontmatter syntax (YAML between --- markers)
  • Check that description is present and meaningful

Edge Cases

Instructions vs Skill? Does this apply to most work, or specific tasks? Most → Instructions. Specific → Skill.

Skill vs Prompt? Both appear as slash commands in chat (type /). Multi-step workflow with bundled assets → Skill. Single focused task with inputs → Prompt.

Skill vs Custom Agent? Same capabilities for all steps → Skill. Need context isolation (subagent returns single output) or different tool restrictions per stage → Custom Agent.

Hooks vs Instructions? Instructions guide agent behavior (non-deterministic). Hooks enforce behavior via shell commands at lifecycle events like PreToolUse or PostToolUse — they can block operations, require approval, or run formatters deterministically. See hooks reference.

Common Pitfalls

Description is the discovery surface. The description field is how the agent decides whether to load a skill, instruction, or agent. If trigger phrases aren't IN the description, the agent won't find it. Use the "Use when..." pattern with specific keywords.

YAML frontmatter silent failures. Unescaped colons in values, tabs instead of spaces, name that doesn't match folder name — all cause silent failures with no error message. Always quote descriptions that contain colons: description: "Use when: doing X".

applyTo: "**" burns context. This means "always included for every file request" — it loads the instruction into the context window on every interaction, even when irrelevant. Use specific globs (**/*.py, src/api/**) unless the instruction truly applies to all files.

FAQ

What does the agent-customization skill do?

WORKFLOW SKILL — Create, update, review, fix, or debug VS Code agent customization files (.instructions.md, .prompt.md, .agent.md, SKILL.md, copilot-instructions.md, AGENTS.md). USE FOR: saving coding preferences; troubleshooting why instructions/skills/agents are ignored or not invoked; configuring applyTo patterns; defining tool restrictions; creating custom agent modes or specialized workflows; packaging domain knowledge; fixing YAML frontmatter syntax. DO NOT USE FOR: general coding questions (use default agent); runtime debugging or error diagnosis; MCP server configuration (use MCP docs directly); VS Code extension development. INVOKES: file system tools (read/write customization files), ask-questions tool (interview user for requirements), subagents for codebase exploration. FOR SINGLE OPERATIONS: For quick YAML frontmatter fixes or creating a single file from a known pattern, edit the file directly — no skill needed.

How do I install agent-customization?

Run npx skills add https://github.com/microsoft/vscode-copilot-chat --skill agent-customization in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/agent-customization/ (personal) or .claude/skills/agent-customization/ (project).

Which AI agents can use agent-customization?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is agent-customization safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains agent-customization?

It is published by microsoft in microsoft/vscode-copilot-chat, and it is an official skill from the maker of the technology it covers. It has 53 recorded installs.

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