/skill-porter

name: skill-porter
description: Converts Claude Code skills to Gemini CLI extensions and vice versa. Use when the user wants to make a skill cross-platform compatible, port a skill between platforms, or create a universal extension that works on both Claude Code and Gemini CLI.
allowed-tools:
  - Read
  - Write
  - Edit
  - Glob
  - Grep
  - Bash

Skill Porter - Cross-Platform Skill Converter

This skill automates the conversion between Claude Code skills and Gemini CLI extensions, enabling true cross-platform AI tool development.

Core Capabilities

Bidirectional Conversion

Convert skills and extensions between platforms while preserving functionality:

**Example requests:**

• "Convert this Claude skill to work with Gemini CLI"
• "Make my Gemini extension compatible with Claude Code"
• "Create a universal version of this skill that works on both platforms"
• "Port the database-helper skill to Gemini"

Smart Platform Detection

Automatically analyzes directory structure to determine source platform:

**Detection criteria:**

• Claude: Presence of `SKILL.md` with YAML frontmatter or `.claude-plugin/marketplace.json`
• Gemini: Presence of `gemini-extension.json` or `GEMINI.md` context file
• Universal: Has both platform configurations

**Example requests:**

• "What platform is this skill built for?"
• "Analyze this extension and tell me what needs to be converted"
• "Is this a Claude skill or Gemini extension?"

Metadata Transformation

Intelligently converts between platform-specific formats:

**Conversions handled:**

• YAML frontmatter ↔ JSON manifest
• `allowed-tools` (whitelist) ↔ `excludeTools` (blacklist)
• Environment variables ↔ settings schema
• MCP server configuration paths
• Platform-specific documentation formats

**Example requests:**

• "Convert the metadata from this Claude skill to Gemini format"
• "Transform the allowed-tools list to Gemini's exclude pattern"
• "Generate a settings schema from these environment variables"

MCP Server Preservation

Maintains Model Context Protocol server configurations across platforms:

**Example requests:**

• "Ensure the MCP server config works on both platforms"
• "Update the MCP server paths for Gemini's ${extensionPath} variable"
• "Validate that the MCP configuration is compatible"

Validation & Quality Checks

Ensures converted output meets platform requirements:

**Validation checks:**

• Required files present (SKILL.md, gemini-extension.json, etc.)
• Valid YAML/JSON syntax
• Correct frontmatter structure
• MCP server paths resolve correctly
• Tool restrictions are valid
• Settings schema is complete

**Example requests:**

• "Validate this converted skill"
• "Check if this Gemini extension meets all requirements"
• "Is this conversion ready to install?"

Conversion Process

When you request a conversion, I will:

1. **Analyze** the source directory structure 2. **Detect** which platform it's built for 3. **Extract** metadata, MCP configuration, and documentation 4. **Transform** the data to target platform format 5. **Generate** required files for target platform 6. **Validate** output meets all requirements 7. **Report** what was converted and any manual steps needed

Platform Differences Handled

File Structure

• **Claude**: `SKILL.md` + `.claude-plugin/marketplace.json`
• **Gemini**: `GEMINI.md` + `gemini-extension.json`
• **Universal**: Both sets of files + shared documentation

Metadata Format

• **Claude**: YAML frontmatter in SKILL.md
• **Gemini**: JSON manifest file
• **Conversion**: Bidirectional YAML ↔ JSON transformation

Tool Restrictions

• **Claude**: `allowed-tools` (whitelist - only listed tools permitted)
• **Gemini**: `excludeTools` (blacklist - listed patterns blocked)
• **Conversion**: Logic inversion with intelligent mapping

Configuration

• **Claude**: Environment variables (user sets before running)
• **Gemini**: Settings schema (prompted during installation)
• **Conversion**: Infer schema from env vars or generate env var docs

MCP Server Paths

• **Claude**: Relative paths from skill directory
• **Gemini**: Uses `${extensionPath}` variable substitution
• **Conversion**: Automatic path transformation

Usage Examples

Convert Claude Skill to Gemini

User: "I have a Claude skill at ./database-helper. Convert it to Gemini."
Claude: I'll analyze the skill and convert it to Gemini format...
- Detected Claude skill (found SKILL.md with frontmatter)
- Extracted metadata and MCP configuration
- Generated gemini-extension.json and GEMINI.md
- Transformed allowed-tools to excludeTools
- Created settings schema from environment variables
✓ Conversion complete! Ready to install with: gemini extensions install ./database-helper

Convert Gemini Extension to Claude

User: "Port my Gemini extension to Claude Code"
Claude: I'll convert this Gemini extension to a Claude skill...
- Detected Gemini extension (found gemini-extension.json)
- Extracted manifest and context file
- Generated SKILL.md with YAML frontmatter
- Created .claude-plugin/marketplace.json
- Converted excludeTools to allowed-tools
✓ Conversion complete! Install with: cp -r ./extension ~/.claude/skills/

Create Universal Extension

User: "Make this skill work on both platforms"
Claude: I'll create a universal extension structure...
- Analyzing current configuration
- Generating both Claude and Gemini files
- Moving shared content to shared/ directory
- Updating MCP server paths for both platforms
✓ Universal extension created! Works with both Claude Code and Gemini CLI

Advanced Features

Pull Request Generation

Create a PR to add dual-platform support to the parent repository:

**Example requests:**

• "Convert this skill and create a PR to add Gemini support"
• "Generate a pull request with the universal version"

Fork and Dual Setup

Create a fork with both platform configurations:

**Example requests:**

• "Fork this repo and set it up for both platforms