/metrics-track

Set up a metrics tracking plan for a project. Defines PostHog event funnel, KPI benchmarks, and kill/iterate/scale decision thresholds based on lean startup principles.

MCP Tools (use if available)

• kb_search(query) — find PostHog methodology, analytics patterns

If MCP tools are not available, fall back to Grep + Read.

Methodology Reference

This skill implements metrics tracking based on lean startup principles:

• Relative metrics vs niche benchmarks — compare against your own trajectory, not vanity averages
• Kill/iterate/scale decision rules — data-driven thresholds for product decisions (see step 7 below)

Steps

1. Parse project from $ARGUMENTS.

   • Read PRD for features, ICP, monetization model.
   • Read CLAUDE.md for stack (iOS/Web/both).
   • If empty: ask via AskUserQuestion.

2. Detect platform:

   • iOS app → PostHog iOS SDK events
   • Web app → PostHog JS SDK events
   • Both → cross-platform identity (shared user ID across platforms)

3. Load PostHog methodology:

   • If MCP available: kb_search("PostHog analytics events funnel identity")
   • Otherwise: check project docs for existing analytics configuration
   • Extract: event naming conventions, identity resolution, funnel pattern

4. Define event funnel based on PRD features:

   Standard funnel stages (adapt per product):

   Awareness → Acquisition → Activation → Revenue → Retention → Referral
   

   Map to concrete events:

   Stage	Event Name	Trigger	Properties
   Awareness	page_viewed	Landing page visit	source, utm_*
   Acquisition	app_installed or signed_up	First install/signup	platform, source
   Activation	core_action_completed	First key action	feature, duration_ms
   Revenue	purchase_completed	First payment	plan, amount, currency
   Retention	session_started	Return visit (D1/D7/D30)	session_number, days_since_install
   Referral	invite_sent	Shared or referred	channel, referral_code

5. Forced reasoning — metrics selection: Before defining KPIs, write out:

   • North Star Metric: The ONE number that matters most (e.g., "weekly active users who completed core action")
   • Leading indicators: What predicts the North Star? (e.g., "activation rate D1")
   • Lagging indicators: What confirms success? (e.g., "MRR", "retention D30")
   • Vanity metrics to AVOID: (e.g., total downloads without activation)

6. Set KPI benchmarks per stage:

   KPI	Target	Kill Threshold	Scale Threshold	Source
   Landing → Signup	3-5%	< 1%	> 8%	Industry avg
   Signup → Activation	20-40%	< 10%	> 50%	Product benchmark
   D1 Retention	25-40%	< 15%	> 50%	Mobile avg
   D7 Retention	10-20%	< 5%	> 25%	Mobile avg
   D30 Retention	5-10%	< 2%	> 15%	Mobile avg
   Trial → Paid	2-5%	< 1%	> 8%	SaaS avg

   Adjust based on product type (B2C vs B2B, free vs paid, mobile vs web).

7. Define decision rules (lean startup kill/iterate/scale):

   ## Decision Framework
   
   **Review cadence:** Weekly (Fridays)
   
   ### KILL signals (any 2 = kill)
   - [ ] Activation rate < {kill_threshold} after 2 weeks
   - [ ] D7 retention < {kill_threshold} after 1 month
   - [ ] Zero organic signups after 2 weeks of distribution
   - [ ] CAC > 3x LTV estimate
   
   ### ITERATE signals
   - [ ] Metrics between kill and scale thresholds
   - [ ] Qualitative feedback suggests product-market fit issues
   - [ ] One stage of funnel is dramatically worse than others
   
   ### SCALE signals (all 3 = scale)
   - [ ] Activation rate > {scale_threshold}
   - [ ] D7 retention > {scale_threshold}
   - [ ] Organic growth > 10% week-over-week
   

8. Generate PostHog implementation snippets:

   For iOS (Swift):

   // Event tracking examples
   PostHogSDK.shared.capture("core_action_completed", properties: [
       "feature": "scan_receipt",
       "duration_ms": elapsed
   ])
   

   For Web (TypeScript):

   // Event tracking examples
   posthog.capture('signed_up', {
       source: searchParams.get('utm_source') ?? 'direct',
       plan: 'free'
   })
   

9. A/B Test Analysis Template:

   Include a reusable template for experiment analysis:

   ## A/B Test: {experiment name}
   
   **Hypothesis:** If we {change}, then {metric} will {improve/decrease} because {reason}.
   **Primary metric:** {metric name}
   **Sample size needed:** {calculated from baseline rate + minimum detectable effect}
   **Duration:** {days} (based on current traffic)
   
   | Variant | Users | Conversions | Rate | vs Control |
   |---------|-------|-------------|------|------------|
   | Control | — | — | —% | — |
   | Test | — | — | —% | +/- X% |
   
   **Statistical significance:** {p-value or confidence interval}
   **Decision:** SHIP variant / KEEP control / EXTEND test / INCONCLUSIVE
   

   Decision rules:

   • p < 0.05 AND positive effect > minimum detectable → SHIP
   • p < 0.05 AND negative effect → KEEP control, investigate why
   • p > 0.05 after full duration → INCONCLUSIVE, check if sample size was sufficient
   • Never peek and decide early — commit to sample size upfront

10. Write metrics plan to docs/metrics-plan.md:

# Metrics Plan: {Project Name}

**Generated:** {YYYY-MM-DD}
**Platform:** {iOS / Web / Both}
**North Star:** {north star metric}

## Event Funnel

| Stage | Event | Properties |
|-------|-------|------------|
{event table from step 4}

## KPIs & Thresholds

| KPI | Target | Kill | Scale |
|-----|--------|------|-------|
{benchmark table from step 6}

## Decision Rules

{framework from step 7}

## Implementation

### PostHog Setup
- Project: {project name} (EU region)
- SDK: {posthog-ios / posthog-js}
- Identity: {anonymous → identified on signup}

### Code Snippets
{snippets from step 8}

## A/B Test Template
{template from step 9}

## Dashboard Template
- Funnel: {stage1} → {stage2} → ... → {stageN}
- Retention: D1 / D7 / D30 cohort chart
- Revenue: MRR trend + trial conversion

---
*Generated by /metrics-track. Implement events, then review weekly.*

11. Output summary — North Star metric, key thresholds, first event to implement, A/B template included.

Notes

• PostHog EU hosting for privacy compliance
• Use $set for user properties, capture for events
• Identity: start anonymous, identify() on signup with user ID
• Cross-platform: same PostHog project, same user ID → unified journey
• Review dashboard weekly, make kill/iterate/scale decision monthly

Common Issues

Wrong platform detected

Cause: Project has both web and iOS indicators. Fix: Skill checks package manifests. If both exist, it generates cross-platform identity setup. Verify the detected platform in the output.

KPI thresholds too aggressive

Cause: Default thresholds are industry averages. Fix: Adjust thresholds in docs/metrics-plan.md based on your niche. B2B typically has lower volume but higher conversion.

PostHog SDK not in project

Cause: Metrics plan generated but SDK not installed. Fix: This skill generates the PLAN only. Install PostHog SDK separately: pnpm add posthog-js (web) or add posthog-ios via SPM (iOS).