Designing CLIs
Overview
Modern CLIs are conversations between human and machine. Great CLIs feel discoverable, responsive, and forgiving. Poor CLIs leave users guessing, waiting, and frustrated.
Core principle: Every CLI interaction should answer: "What happened? What can I do? What's next?"
When to Use
Building:
- Creating new CLI commands or tools
- Designing output format, error messages, progress indicators
- Planning CLI architecture (flags, subcommands, interaction model)
Improving:
- Enhancing existing CLI user experience
- Adding features to existing commands
- Making CLI "less confusing" or "easier to use"
Reviewing:
- Auditing CLI code for UX issues
- Responding to user complaints about difficulty
- Troubleshooting discoverability problems
Quick Decision Framework
| Working On |
Read This |
| New CLI under time pressure |
practical-patterns.md (Priority Checklist) |
| Adding to existing CLI |
practical-patterns.md (Working with Existing CLIs) |
| Fixing "confusing" CLI |
practical-patterns.md (CLI UX Audit Checklist) |
| Command structure, flags |
ux-principles.md (Familiarity, Discoverability) |
| Output formatting |
visual-techniques.md (Layout, Spacing, Color) |
| Error messages, help text |
practical-patterns.md (Error Message Patterns) |
| Overall architecture |
ux-principles.md (complete overview) |
The Six UX Principles
- Familiarity - Use known conventions (--help, --version, verb-noun)
- Discoverability - Guide users (help text, prompts, examples)
- Feedback - Show what's happening (progress, confirmations, state)
- Clarity - Structure output (spacing, alignment, hierarchy)
- Flow - Minimize friction (shortcuts, defaults, scriptability)
- Forgiveness - Handle errors gracefully (clear messages, suggestions, safety)
See ux-principles.md for detailed guidance and examples.
The Five Visual Techniques
- Color - Semantic meaning (green=success, red=error, yellow=warning)
- Spacing - Visual grouping (blank lines, indentation, alignment)
- Layout - Structured regions (panels, blocks, persistent areas)
- Symbols - Fast signifiers (✓ ✗ ⚠ →, checkboxes, progress indicators)
- Structured Feedback - Narrative output (phases, lists, visible progress)
See visual-techniques.md for implementation patterns.
Common Mistakes
❌ Silent operations - No feedback during slow operations
✅ Show progress, confirmations, or at minimum "Working..."
❌ Cryptic errors without guidance - "Error: invalid input"
✅ Explain what's wrong, what's valid, how to fix: "Error: Invalid environment 'production'. Valid: dev, staging, prod"
❌ No --help text - Forces users to read docs or source
✅ Every command supports --help with usage and examples
❌ Wrong exit codes - Always returns 0, breaks scripting
✅ 0 for success, 1 for errors
❌ Color-only information - Inaccessible without color support
✅ Always pair color with text/symbols, support --no-color
❌ Walls of unstructured text - Dense output hard to scan
✅ Use spacing, alignment, hierarchy to structure information
Priority Under Time Pressure
When building CLI urgently, include these first (high impact, low effort):
- --help flag (2 minutes) - Include usage, examples, common flags
- Exit codes (1 minute) - 0=success, 1=error, enables CI/CD
- Clear errors (5 minutes) - What happened + what's valid + how to fix
- Progress feedback (3 minutes) - Show activity during slow operations
Skip initially (lower priority):
- Color schemes (polish, not function)
- Advanced formatting (tables, columns)
- Multiple output formats (JSON, YAML, etc.)
Cross-References
Detailed guidance:
- practical-patterns.md - Checklists, templates, decision trees
- ux-principles.md - Principles with real-world examples
- visual-techniques.md - Implementation patterns for terminal output
- reading-list.md - Sources and deeper learning
Research materials:
- research/ - Original blog-style documentation and analysis
1---2name: cli-design3description: Use when building, improving, or reviewing command-line interfaces for better user experience - before implementing commands/output/errors, when users report confusion or frustration, or when CLI feels hard to use - provides UX principles, visual design techniques, and practical patterns for creating discoverable, delightful CLIs4---56# Designing CLIs78## Overview910Modern CLIs are conversations between human and machine. Great CLIs feel discoverable, responsive, and forgiving. Poor CLIs leave users guessing, waiting, and frustrated.1112**Core principle:** Every CLI interaction should answer: "What happened? What can I do? What's next?"1314## When to Use1516**Building:**17- Creating new CLI commands or tools18- Designing output format, error messages, progress indicators19- Planning CLI architecture (flags, subcommands, interaction model)2021**Improving:**22- Enhancing existing CLI user experience23- Adding features to existing commands24- Making CLI "less confusing" or "easier to use"2526**Reviewing:**27- Auditing CLI code for UX issues28- Responding to user complaints about difficulty29- Troubleshooting discoverability problems3031## Quick Decision Framework3233| Working On | Read This |34|------------|-----------|35| New CLI under time pressure | practical-patterns.md (Priority Checklist) |36| Adding to existing CLI | practical-patterns.md (Working with Existing CLIs) |37| Fixing "confusing" CLI | practical-patterns.md (CLI UX Audit Checklist) |38| Command structure, flags | ux-principles.md (Familiarity, Discoverability) |39| Output formatting | visual-techniques.md (Layout, Spacing, Color) |40| Error messages, help text | practical-patterns.md (Error Message Patterns) |41| Overall architecture | ux-principles.md (complete overview) |4243## The Six UX Principles44451. **Familiarity** - Use known conventions (--help, --version, verb-noun)462. **Discoverability** - Guide users (help text, prompts, examples)473. **Feedback** - Show what's happening (progress, confirmations, state)484. **Clarity** - Structure output (spacing, alignment, hierarchy)495. **Flow** - Minimize friction (shortcuts, defaults, scriptability)506. **Forgiveness** - Handle errors gracefully (clear messages, suggestions, safety)5152See ux-principles.md for detailed guidance and examples.5354## The Five Visual Techniques55561. **Color** - Semantic meaning (green=success, red=error, yellow=warning)572. **Spacing** - Visual grouping (blank lines, indentation, alignment)583. **Layout** - Structured regions (panels, blocks, persistent areas)594. **Symbols** - Fast signifiers (✓ ✗ ⚠ →, checkboxes, progress indicators)605. **Structured Feedback** - Narrative output (phases, lists, visible progress)6162See visual-techniques.md for implementation patterns.6364## Common Mistakes6566❌ **Silent operations** - No feedback during slow operations67✅ Show progress, confirmations, or at minimum "Working..."6869❌ **Cryptic errors without guidance** - "Error: invalid input"70✅ Explain what's wrong, what's valid, how to fix: "Error: Invalid environment 'production'. Valid: dev, staging, prod"7172❌ **No --help text** - Forces users to read docs or source73✅ Every command supports --help with usage and examples7475❌ **Wrong exit codes** - Always returns 0, breaks scripting76✅ 0 for success, 1 for errors7778❌ **Color-only information** - Inaccessible without color support79✅ Always pair color with text/symbols, support --no-color8081❌ **Walls of unstructured text** - Dense output hard to scan82✅ Use spacing, alignment, hierarchy to structure information8384## Priority Under Time Pressure8586When building CLI urgently, include these first (high impact, low effort):87881. **--help flag** (2 minutes) - Include usage, examples, common flags892. **Exit codes** (1 minute) - 0=success, 1=error, enables CI/CD903. **Clear errors** (5 minutes) - What happened + what's valid + how to fix914. **Progress feedback** (3 minutes) - Show activity during slow operations9293Skip initially (lower priority):94- Color schemes (polish, not function)95- Advanced formatting (tables, columns)96- Multiple output formats (JSON, YAML, etc.)9798## Cross-References99100**Detailed guidance:**101- practical-patterns.md - Checklists, templates, decision trees102- ux-principles.md - Principles with real-world examples103- visual-techniques.md - Implementation patterns for terminal output104- reading-list.md - Sources and deeper learning105106**Research materials:**107- research/ - Original blog-style documentation and analysis
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