Confidence Check — Claude Code skill: score before you code

---
name: Confidence Check
description: Pre-implementation confidence assessment (≥90% required). Use before starting any implementation to verify readiness with duplicate check, architecture compliance, official docs verification, OSS references, and root cause identification.
---

# Confidence Check Skill

## Purpose

Prevents wrong-direction execution by assessing confidence **BEFORE** starting implementation.

**Requirement**: ≥90% confidence to proceed with implementation.

**Test Results** (2025-10-21):
- Precision: 1.000 (no false positives)
- Recall: 1.000 (no false negatives)
- 8/8 test cases passed

## When to Use

Use this skill BEFORE implementing any task to ensure:
- No duplicate implementations exist
- Architecture compliance verified
- Official documentation reviewed
- Working OSS implementations found
- Root cause properly identified

## Confidence Assessment Criteria

Calculate confidence score (0.0 - 1.0) based on 5 checks:

### 1. No Duplicate Implementations? (25%)

**Check**: Search codebase for existing functionality

```bash
# Use Grep to search for similar functions
# Use Glob to find related modules
```

✅ Pass if no duplicates found
❌ Fail if similar implementation exists

### 2. Architecture Compliance? (25%)

**Check**: Verify tech stack alignment

- Read `CLAUDE.md`, `PLANNING.md`
- Confirm existing patterns used
- Avoid reinventing existing solutions

✅ Pass if uses existing tech stack (e.g., Supabase, UV, pytest)
❌ Fail if introduces new dependencies unnecessarily

### 3. Official Documentation Verified? (20%)

**Check**: Review official docs before implementation

- Use Context7 MCP for official docs
- Use WebFetch for documentation URLs
- Verify API compatibility

✅ Pass if official docs reviewed
❌ Fail if relying on assumptions

### 4. Working OSS Implementations Referenced? (15%)

**Check**: Find proven implementations

- Use Tavily MCP or WebSearch
- Search GitHub for examples
- Verify working code samples

✅ Pass if OSS reference found
❌ Fail if no working examples

### 5. Root Cause Identified? (15%)

**Check**: Understand the actual problem

- Analyze error messages
- Check logs and stack traces
- Identify underlying issue

✅ Pass if root cause clear
❌ Fail if symptoms unclear

## Confidence Score Calculation

```
Total = Check1 (25%) + Check2 (25%) + Check3 (20%) + Check4 (15%) + Check5 (15%)

If Total >= 0.90:  ✅ Proceed with implementation
If Total >= 0.70:  ⚠️  Present alternatives, ask questions
If Total < 0.70:   ❌ STOP - Request more context
```

## Output Format

```
📋 Confidence Checks:
   ✅ No duplicate implementations found
   ✅ Uses existing tech stack
   ✅ Official documentation verified
   ✅ Working OSS implementation found
   ✅ Root cause identified

📊 Confidence: 1.00 (100%)
✅ High confidence - Proceeding to implementation
```

## Implementation Details

The TypeScript implementation is available in `confidence.ts` for reference, containing:

- `confidenceCheck(context)` - Main assessment function
- Detailed check implementations
- Context interface definitions

## ROI

**Token Savings**: Spend 100-200 tokens on confidence check to save 5,000-50,000 tokens on wrong-direction work.

**Success Rate**: 100% precision and recall in production testing.