Extension Types

Understanding the different types of capabilities you can add through Qwen Code extensions

Extension Types

Qwen Code extensions support five main types of capabilities. Each type serves a different purpose and can be combined within a single extension.

MCP Servers

Model Context Protocol (MCP) servers add new tools that the AI can use to interact with external services, APIs, or perform specialized operations.

What are MCP Servers?

• Standalone processes that communicate via stdio
• Provide tools (functions) the AI can call
• Can expose prompts and resources
• Run continuously during your session

Use Cases

• Fetch data from external APIs
• Interact with databases
• Control external services (deployment, monitoring)
• Process files in specialized formats
• Integrate with third-party tools

Example

{
  "name": "github-tools",
  "version": "1.0.0",
  "mcpServers": {
    "github": {
      "command": "node",
      "args": ["${extensionPath}${/}dist${/}server.js"],
      "cwd": "${extensionPath}",
      "env": {
        "GITHUB_TOKEN": "${GITHUB_TOKEN}"
      }
    }
  }
}

Learn more: Creating MCP Server Extensions

Custom Commands

Custom commands are shortcuts for complex prompts that can be invoked with slash syntax.

What are Custom Commands?

• Markdown files with optional YAML frontmatter
• Can include template variables with {{args}}
• Can execute shell commands with !{command}
• Support nested directory structure for organization

Use Cases

• Create project-specific workflows
• Package common development patterns
• Automate repetitive tasks
• Build domain-specific helpers

Example

---
description: Search for a pattern in code and summarize findings
---

Please summarize the findings for the pattern `{{args}}`.

Search Results:
!{grep -r {{args}} .}

Invoked as: /fs:grep-code "TODO"

Learn more: Creating Command Extensions

Skills

Skills are specialized capabilities that the AI can automatically invoke when relevant to the user’s request.

What are Skills?

• Model-invoked capabilities (not user-invoked)
• Defined in SKILL.md files with YAML frontmatter
• Discovered automatically when extension is loaded
• Available via /skills command to view/manage

Use Cases

• Add domain-specific expertise
• Provide specialized analysis capabilities
• Enable automatic workflow handling
• Extend AI reasoning for specific tasks

Example

---
name: code-analyzer
description: Analyzes code structure and provides insights about complexity and dependencies
---

# Code Analyzer

When analyzing code, focus on:
- Code complexity and maintainability
- Dependencies and coupling
- Potential performance issues

Learn more: Creating Skill Extensions

Subagents (Agents)

Subagents are specialized AI assistants configured for specific tasks with their own system prompts and tool access.

What are Subagents?

• Markdown or YAML files defining agent behavior
• YAML frontmatter specifies name, tools, model config
• Content contains system prompt instructions
• Appear in agent manager dialog

Use Cases

• Create task-specific AI experts
• Define consistent behavior patterns
• Package reusable AI workflows
• Share specialized assistants

Example

---
name: refactoring-expert
description: Specialized in code refactoring and improving code quality
color: blue
tools:
  - Read
  - Write
  - Grep
modelConfig:
  model: qwen3-coder-plus
---

You are a refactoring specialist focused on improving code quality.

Your expertise includes:
- Identifying code smells
- Applying SOLID principles
- Improving readability

Learn more: Creating Agent Extensions

Context Providers

Context providers supply persistent context to the model through a QWEN.md file that’s loaded in every session.

What are Context Providers?

• Markdown file loaded into system context
• Always available to the AI
• Useful for instructions and documentation
• Can describe extension capabilities

Use Cases

• Provide usage instructions for extension tools
• Define behavioral guidelines
• Document project conventions
• Add domain knowledge

Example

# Database Query Assistant

You have access to database query tools. When the user asks about data:

1. Use the `query_database` tool to fetch information
2. Format results in clear tables
3. Explain any complex queries

Always verify table names before querying.

Learn more: Creating Context Provider Extensions

Settings

Extension settings allow you to configure API keys, credentials, and other values securely.

What are Settings?

• Defined in qwen-extension.json
• Prompted during installation
• Stored securely (sensitive values in keychain)
• Passed as environment variables to MCP servers

Use Cases

• Store API keys and tokens
• Configure service endpoints
• Set user preferences
• Provide credentials

Example

{
  "name": "api-extension",
  "version": "1.0.0",
  "settings": [
    {
      "name": "API Key",
      "description": "Your API key for the service",
      "envVar": "MY_API_KEY",
      "sensitive": true
    },
    {
      "name": "API Endpoint",
      "description": "Base URL for the API",
      "envVar": "API_ENDPOINT",
      "sensitive": false
    }
  ]
}

Manage with:

qwen extensions settings set my-extension "API Key"
qwen extensions settings list my-extension

Combining Extension Types

You can combine multiple types in a single extension:

my-complete-extension/
├── qwen-extension.json       # Defines MCP servers and settings
├── QWEN.md                   # Provides context
├── commands/
│   ├── deploy.md            # Custom command
│   └── test.md              # Custom command
├── skills/
│   └── analyzer/
│       └── SKILL.md         # Skill
└── agents/
    └── expert.md            # Subagent

{
  "name": "my-complete-extension",
  "version": "1.0.0",
  "mcpServers": {
    "tools": {
      "command": "node",
      "args": ["${extensionPath}${/}dist${/}server.js"]
    }
  },
  "contextFileName": "QWEN.md",
  "commands": "commands",
  "skills": "skills",
  "agents": "agents",
  "settings": [
    {
      "name": "Service Token",
      "description": "Authentication token",
      "envVar": "SERVICE_TOKEN",
      "sensitive": true
    }
  ]
}

This creates a comprehensive extension with tools, commands, AI capabilities, and secure configuration.

Next Steps

• Creating Your First Extension
• MCP Server Extensions
• Command Extensions
• Skill Extensions
• Agent Extensions
• Context Providers