OpenCode Lazy Loader Plugin

This is the OpenCode plugin that lazy-loads skill-embedded MCP servers. It lets skills bundle their own MCP servers so they can be loaded on-demand instead of being configured globally.

Note: This package was renamed from opencode-embedded-skill-mcp to opencode-lazy-loader. If you still have the old package, upgrade to the new name.

This is a standalone OpenCode plugin that enables skills to bundle and manage their own Model Context Protocol (MCP) servers, then lazy-load them on demand.

This allows skills to bring their own tools, resources, and prompts without requiring manual server configuration in opencode.json.

Why use this?

• Plug-and-Play Skills: Skills bring their own tools. No need to manually register servers in your global config.
• Cleaner Context: Tools are loaded on-demand only when the skill is active, keeping your agent's context window focused and efficient.
• Team Portability: Commit skills to your project repo; anyone with the plugin gets the tools automatically.
• Efficient Resources: Servers start only when used and shut down automatically after 5 minutes of inactivity.

Technical Features

• Skill-Embedded MCPs: Configure MCP servers directly within skill definitions (markdown frontmatter or mcp.json).
• Zero Configuration: Skills manage their own MCP connections; just load the skill and use the tools.
• Connection Management:
  • Connection pooling per session/skill/server.
  • Lazy connection initialization (connects on first use).
  • Automatic idle cleanup (disconnects after 5 minutes of inactivity).
  • Session-scoped resource cleanup.
• Environment Variable Support: Full support for ${VAR} and ${VAR:-default} expansion in MCP configurations.

Installation

Deprecation notice: The package was renamed from opencode-embedded-skill-mcp to opencode-lazy-loader. If you installed the old name, update to the new package.

Add the plugin to your opencode.json:

{
  "plugin": ["opencode-lazy-loader"]
}

Or install it locally:

{
  "plugin": ["./path/to/opencode-lazy-loader"]
}

Quick Start

This repo includes a working example skill. After installing the plugin, try:

skill(name="playwright-example")

Then use the embedded MCP:

skill_mcp(mcp_name="playwright", tool_name="browser_navigate", arguments='{"url": "https://example.com"}')

See .opencode/skill/playwright-example/SKILL.md for the full example.

Usage

1. Create a Skill with Embedded MCP

You can define MCP servers in the skill's YAML frontmatter:

~/.config/opencode/skill/my-skill/SKILL.md

---
name: browser-automation
description: "A skill for automating browser interactions"
mcp:
  playwright:
    command: ["npx", "-y", "@playwright/mcp@latest"]
---

# Browser Automation

This skill provides browser automation tools via the `playwright` MCP.

Alternatively, place an mcp.json file in the skill directory:

~/.config/opencode/skill/browser-automation/mcp.json

{
  "mcpServers": {
    "playwright": {
      "command": ["npx", "-y", "@playwright/mcp@latest"]
    }
  }
}

2. Load the Skill

In OpenCode:

skill(name="browser-automation")

Pro Tip: You don't always need to call the tool explicitly. Just ask for the skill by name in chat, and OpenCode will usually find and load it for you:

"Use the browser-automation skill to take a screenshot of google.com"

The plugin will load the skill and discover the capabilities of the embedded MCP server.

3. Use MCP Tools

Invoke tools, read resources, or get prompts using skill_mcp:

skill_mcp(mcp_name="playwright", tool_name="screenshot", arguments='{"url": "https://google.com"}')

Tools Provided

skill

Loads a skill and displays its instructions along with any available MCP capabilities (tools, resources, prompts).

• name: The name of the skill to load.

skill_mcp

Invokes an operation on a skill-embedded MCP server.

• mcp_name: The name of the MCP server (defined in the skill config).
• tool_name: (Optional) The name of the tool to call.
• resource_name: (Optional) The URI of the resource to read.
• prompt_name: (Optional) The name of the prompt to get.
• arguments: (Optional) JSON string of arguments for the operation.
• grep: (Optional) Regex pattern to filter the output.

Configuration Format

The MCP configuration supports multiple formats for compatibility with both OpenCode and oh-my-opencode:

interface McpServerConfig {
  // Command formats (both supported):
  command: string | string[]   // Array: ["npx", "-y", "@some/mcp"] or String: "npx"
  args?: string[]              // Used with string command: ["-y", "@some/mcp"]
  
  // Environment variable formats (both supported):
  env?: Record<string, string> | string[]  // Object: { "KEY": "val" } or Array: ["KEY=val"]
}

Examples

Object format for env (recommended):

{
  "my-server": {
    "command": "npx",
    "args": ["-y", "@some/mcp-server"],
    "env": {
      "API_KEY": "${MY_API_KEY}",
      "DEBUG": "true"
    }
  }
}

Array format for env (OpenCode style):

{
  "my-server": {
    "command": ["npx", "-y", "@some/mcp-server"],
    "env": ["API_KEY=${MY_API_KEY}", "DEBUG=true"]
  }
}

Example Skill

Here's a complete example of a skill with an embedded MCP server (from .opencode/skill/playwright-example/SKILL.md):

---
name: playwright-example
description: Browser automation skill for web testing, scraping, and interaction. Use for end-to-end testing, screenshots, and browser automation tasks.
argument-hint: describe what you want to do (e.g., "take a screenshot of homepage", "test login flow", "fill out a form")
mcp:
  playwright:
    command: ["npx", "-y", "@playwright/mcp@latest"]
---

# Playwright Browser Automation

This skill provides browser automation capabilities via the Playwright MCP server.

## Available Operations

- **Navigation**: Navigate to URLs, go back/forward, reload pages
- **Screenshots**: Capture full page or element screenshots
- **Interactions**: Click, type, select, hover, and other user interactions
- **Forms**: Fill out forms, submit data, handle file uploads

## Example Tasks

- "Navigate to the login page and take a screenshot"
- "Fill out the registration form with test data"
- "Extract all product names from the catalog page"

License

MIT