Ask User Question

Implementing Skills with AskUserQuestion

How to author skills that use the AskUserQuestion tool for interactive user input, decisions, and guided workflows.

Official Tool Purpose

From Claude Code system prompt:

Use AskUserQuestion to:

1. Gather user preferences or requirements - Understand what user wants
2. Clarify ambiguous instructions - Ask when instructions are unclear
3. Get decisions on implementation choices - Multiple valid approaches exist
4. Offer choices about what direction to take - User picks path forward

Key Capabilities:

• Users always see "Other" option for custom text input
• multiSelect: true allows selecting multiple answers
• Put recommended option first, labeled with "(Recommended)"

Important: Don't use to ask "Is my plan ready?" or similar meta-questions. Use in-band questions only for actual decisions.

How It Works in Skills

Response Format:

{
  "questions": [...original questions...],
  "answers": {
    "Question text": "selected option OR custom text",
    "Another question": "answer"
  }
}

Critical Rule: Custom text appears in answers directly, not as "Other"

answers["Framework?"] = "angular"    ✅ (user typed)
answers["Framework?"] = "Other"      ❌ (never this)

Hard Constraints

Tool Limits (Claude Code enforced):

• Max 1-4 questions per call
• Min 2, Max 4 options per question
• "Other" is automatic (never include in options list)
• Max header: 12 characters
• Max option label: varies but aim for 1-5 words
• Max description: 1-2 sentences recommended

"Other" Behavior:

• Always present automatically
• Users can type any custom text
• Custom text returned as answer value (not "Other")

Example:

answers["Framework?"] = "angular"     ✅ (user typed "angular")
answers["Framework?"] = "Other"       ❌ (never this)

How to Wire AskUserQuestion Into a Skill

Pattern 1: Prose Question (Typical)

Ask in natural language, users respond freely:

## Step 1: Ask User for Input

**What are we building?**

Describe the feature or change you want to make.

(I'll ask follow-up questions if I need clarification)

[User responds with description]

## Step 2: Follow-Up If Needed

Based on their response, ask 1-2 clarifying questions:
- "Is this a new feature or updating existing?"
- "What's the expected outcome?"

[User responds]

## Step 3: Process Answers

Use their responses to inform next steps...

Pattern 2: Structured Options (When Choices Matter)

Use tool when user must select from specific options:

## Step 1: Ask for Configuration Choice

Use AskUserQuestion tool:

**Question 1:**
- Text: "Which option?"
- Header: "Choice"
- Options:
  - Label: "Option A"
    Description: "What this does, trade-offs"
  - Label: "Option B"
    Description: "Alternative approach"

[User selects or types "Other" for custom]

## Step 2: Process Answer

The response provides:
- answers["Which option?"] = user's selection

Based on answer:
- If "Option A": Do X
- If "Option B": Do Y
- If custom text: Do Z

## Step 3: Continue

Proceed with workflow...

Progressive Disclosure Pattern

CRITICAL: Ask ONE question, wait for response, THEN ask next.

## Question 1: Gather Type

Ask: "What type of project?"
Options: Web, Mobile, CLI

[User answers]

## Question 2: Framework (Conditional)

Based on answer to Q1:
- If Web: Ask "Frontend framework?"
- If Mobile: Ask "Platform?"
- If CLI: Ask "Language?"

[User answers]

## Question 3: Confirmation

Show summary and ask: "Proceed?"
Options: Yes, No, Edit

[Continue based on answer]

Defining Questions in Skills

Pattern 1: Prose with Guidance (Recommended)

Ask questions in natural language with examples. No options needed:

## What are we building?

Please describe the feature or change.

(Be as specific as you like — I'll ask follow-ups if needed)

Or with guidance:

## Do you have any visuals to reference?

- Mockups or wireframes
- Screenshots of similar features
- Examples from other apps

(Paste images, share file paths, or say "none")

This pattern:

• ✅ Feels natural to users
• ✅ Allows truly open input
• ✅ No constraint on number of options
• ✅ Users can respond with anything

Pattern 2: Structured Options (When Choosing Matters)

Use tool options when user must select from specific choices:

**Question: Database Selection**
- Text: "Which database for this project?"
- Header: "Database"  (max 12 chars)
- Options:
  - Label: "PostgreSQL"
    Description: "Relational, ACID compliant, best for complex queries"
  - Label: "MongoDB"
    Description: "Document-based, flexible schema, rapid iteration"
  - Label: "Redis"
    Description: "In-memory, very fast, ideal for caching"

Constraints for this pattern:

• Min 2, Max 4 options per question
• "Other" automatic for custom input
• Users can select one (or multiple if multiSelect: true)

Use when:

• Multiple mutually-exclusive choices exist
• Each option leads to different workflow
• You want to guide without forcing

Pattern 3: Multi-Select Options

When users should enable/select multiple independent items:

**Question: Which features to enable?**
- Header: "Features"
- multiSelect: true
- Options:
  - "Logging" (Operation logs for debugging)
  - "Metrics" (Performance monitoring)
  - "Alerts" (Error notifications)
  - "Backups" (Automatic data backups)

Response: answers["Features?"] = "Logging, Metrics" (joined with ", ")

Processing Responses

Basic Response Handling

The tool returns:

{
  "questions": [...],
  "answers": {
    "Which database?": "PostgreSQL"
  }
}

In skill body:

Based on the answer to "Which database?":
- If "PostgreSQL": Set up relational database
- If "MongoDB": Set up document database
- If "Redis": Set up in-memory cache
- If custom text: Configure for custom database name

Then proceed with configuration...

Checking Multiple Answers

From response:
- answers["Database?"] = "PostgreSQL"
- answers["Environment?"] = "production"
- answers["Features?"] = "Logging, Metrics"

In skill:

Database: PostgreSQL (check: is this supported?)
Environment: production (check: validate settings for prod)
Features: Split by ", " and enable each

If any validation fails:
  Log error
  Ask user to reconfigure
  Return to questioning phase

Handling Free-Text Answers

When users select "Other" and type custom input, you need to handle it properly.

Pattern: Check if answer is a known option or custom text, then route accordingly.

If user selected "Other" and typed "custom-framework":

answers["Framework?"] = "custom-framework"

In skill:

Check if "custom-framework" is in known frameworks:
  - If yes: use framework-specific setup
  - If no: use generic setup with warning

Log: "Using custom framework: custom-framework"
Proceed with generic configuration...

See references/free-text-input-patterns.md for complete patterns for handling custom input including validation, generic fallbacks, and user feedback.

When to Use Each Pattern

Use Prose Questions When:

• Scope is open-ended (user describes feature, context, etc.)
• You need true free-form input
• Multiple follow-ups will be needed
• No specific options constrain the answer
• Examples: "What are we building?", "Describe the problem"

Use Structured Options When:

• User must choose from specific alternatives
• Each option leads to different workflow/configuration
• You want to guide without forcing
• Examples: "Which database?", "Enable monitoring?" (Yes/No)

Mixed Approach:

Start with prose for context/understanding, then use structured options for specific decisions:

Step 1: Ask "What are we building?" (prose)
Step 2: Ask "Which database?" (structured options)
Step 3: Ask "Which features?" (multi-select options)

Question Design (For Structured Options)

When using predefined options:

• Be specific: "Which database for this project?" (not "Database?")
• Provide context: "Relational, ACID compliant, best for complex queries"
• Show trade-offs: "Fast for reads, slower for writes, good for analytics"
• Mutually exclusive: Options should be distinct (unless multiSelect)
• Consistent format: Same capitalization, length (~1-2 sentences), detail level

See references/skill-patterns.md for complete question design examples.

Dynamic Questions Pattern

How to ask different questions based on previous answers:

## Step 1: Initial Question

Ask: "Application type?"
Options: Web, Mobile, CLI

[Get answer]

## Step 2: Conditional Question

If answer == "Web":
  Ask: "Frontend framework?"
  Options: React, Vue, Svelte

If answer == "Mobile":
  Ask: "Platform?"
  Options: iOS, Android, Cross-platform

If answer == "CLI":
  Ask: "Language?"
  Options: Python, Go, Rust

[Get answer]

## Step 3: More Conditional Questions

Based on BOTH previous answers:
If Web + React:
  Ask: "State management?"
  Options: Redux, Context, Zustand

If Web + Vue:
  Ask: "State management?"
  Options: Pinia, Vuex

[Continue...]

Error Handling in Skills

Check if Response Received

If AskUserQuestion fails or no answers:

Log error: "Failed to gather responses"
Show: "Please try again or provide configuration manually"
Exit

(Or restart the questioning phase)

Validate Answer Format

If question expects "port number":
  answers["Port?"] could be:
  - "8080" (valid)
  - "invalid" (needs validation)
  - "12345" (out of range)

Validate before using:
  Parse as number
  Check range (1-65535)
  If invalid: Ask user to reconfigure

Handle Empty Answers

If answers["Required field?"] is empty or missing:

Log: "No answer provided for required field"
Ask user to reconfigure

Don't proceed with empty critical answers

Common Limitations & Workarounds

See references/advanced-patterns.md for detailed workarounds for common constraint scenarios (max questions, max options, dependent options, pre-populating answers).

Response Processing Workflow

Typical skill using AskUserQuestion:

1. Describe what you're asking
   "Let's configure your database"

2. Ask Question 1
   Call AskUserQuestion with 1 question

3. Get Response
   Extract answers from response object

4. Validate
   Check format, compatibility, ranges

5. Ask Question 2 (if conditional)
   Based on Q1 answer, ask Q2

6. Get Response & Validate

7. Process All Answers
   - Check compatibility across answers
   - Apply configuration
   - Generate outputs

8. Confirm
   Ask: "Does this look right?"
   If Yes: Proceed
   If No: Restart from Q1

Writing About AskUserQuestion in Skills

See references/skill-patterns.md for guidance on documenting AskUserQuestion in skill descriptions, body content, and custom input support.

Testing Skills with AskUserQuestion

See references/robust-skills.md for testing validation patterns and common test cases (valid options, custom text, invalid input, edge cases).

Key Takeaways

✅ Max constraints: 1-4 questions, 2-4 options, 12-char header

✅ Progressive disclosure: One question → wait → next question

✅ Custom input: "Other" automatic, custom text goes in answers

✅ Conditional: Ask different Q2 based on Q1 answer

✅ Validation: Always check answers before using

✅ Response format: Extract from answers object

✅ Error handling: Check for missing/invalid answers

❌ Don't: Combine multiple questions, use >4 options, include "Other" in options

See references/common-mistakes.md for detailed anti-patterns and how to avoid them.

Plan Mode: Clarifying Decisions vs. Meta-Questions

Use AskUserQuestion in plan mode to clarify real implementation decisions (database choice, monitoring config), not meta-questions ("Is my plan ready?"). For plan approval, use the plan approval tool instead. See references/advanced-patterns.md for detailed guidance.

Based on: Claude Code system prompt (tool-description-askuserquestion.md) Source: https://github.com/Piebald-AI/claude-code-system-prompts Last updated: 2026-02-25 | Version: 1.0.0