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"
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?"
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:
- Analyze the source directory structure
- Detect which platform it's built for
- Extract metadata, MCP configuration, and documentation
- Transform the data to target platform format
- Generate required files for target platform
- Validate output meets all requirements
- Report what was converted and any manual steps needed
File Structure
- Claude:
SKILL.md + .claude-plugin/marketplace.json
- Gemini:
GEMINI.md + gemini-extension.json
- Universal: Both sets of files + shared documentation
- Claude: YAML frontmatter in SKILL.md
- Gemini: JSON manifest file
- Conversion: Bidirectional YAML ↔ JSON transformation
- 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"
- "Create a dual-platform fork I can use with both CLIs"
Validation Only
Check compatibility without converting:
Example requests:
- "Validate this skill's conversion to Gemini"
- "Check if this extension can be ported to Claude"
- "What needs to change to make this universal?"
Configuration
This skill operates directly on filesystem directories and doesn't require external configuration. It uses:
- File system access to read and write skill/extension files
- Git operations for PR and fork features
- GitHub CLI (
gh) for repository operations
Safety Features
- Non-destructive: Creates new files, doesn't modify source unless explicitly requested
- Validation: Checks output before completion
- Reporting: Clear summary of changes made
- Rollback friendly: All changes are standard file operations
Limitations
Some aspects may require manual review:
- Custom slash commands (platform-specific syntax)
- Complex MCP server configurations with multiple servers
- Platform-specific scripts that don't translate directly
- Edge cases in tool restriction mapping
These will be flagged in the conversion report.
Technical Details
Claude → Gemini (Whitelist → Blacklist):
- Analyze allowed-tools list
- Generate exclude patterns for all other tools
- Special handling for wildcard permissions
Gemini → Claude (Blacklist → Whitelist):
- List all available tools
- Remove excluded tools
- Generate allowed-tools list
Settings Inference
When converting Claude → Gemini, environment variables in MCP config become settings:
// MCP env var
"env": { "DB_HOST": "${DB_HOST}" }
// Becomes Gemini setting
"settings": [{
"name": "DB_HOST",
"description": "Database host",
"default": "localhost"
}]
Claude uses relative paths, Gemini uses variables:
// Claude
"args": ["mcp-server/index.js"]
// Gemini
"args": ["${extensionPath}/mcp-server/index.js"]
For implementation details, see the repository at https://github.com/jduncan-rva/skill-porter