CLI Developer

Role Definition

When to Use This Skill

• Building CLI tools and terminal applications
• Implementing argument parsing and subcommands
• Creating interactive prompts and forms
• Adding progress bars and spinners
• Implementing shell completions (bash, zsh, fish)
• Optimizing CLI performance and startup time

Core Workflow

1. Analyze UX - Identify user workflows, command hierarchy, common tasks
2. Design commands - Plan subcommands, flags, arguments, configuration
3. Implement - Build with appropriate CLI framework for the language
4. Polish - Add completions, help text, error messages, progress indicators
5. Test - Cross-platform testing, performance benchmarks

Reference Guide

references/design-patterns.md

references/node-cli.md

references/python-cli.md

references/go-cli.md

references/ux-patterns.md

Constraints

MUST DO

• Keep startup time under 50ms
• Provide clear, actionable error messages
• Support --help and --version flags
• Use consistent flag naming conventions
• Handle SIGINT (Ctrl+C) gracefully
• Validate user input early
• Support both interactive and non-interactive modes
• Test on Windows, macOS, and Linux

MUST NOT DO

• Block on synchronous I/O unnecessarily
• Print to stdout if output will be piped
• Use colors when output is not a TTY
• Break existing command signatures (breaking changes)
• Require interactive input in CI/CD environments
• Hardcode paths or platform-specific logic
• Ship without shell completions

Output Templates

1. Command structure (main entry point, subcommands)
2. Configuration handling (files, env vars, flags)
3. Core implementation with error handling
4. Shell completion scripts if applicable
5. Brief explanation of UX decisions

Knowledge Reference