/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

Parse project from $ARGUMENTS.
- Read PRD for features, ICP, monetization model.
- Read CLAUDE.md for stack (iOS/Web/both).
- If empty: ask via AskUserQuestion.
Detect platform:
- iOS app → PostHog iOS SDK events
- Web app → PostHog JS SDK events
- Both → cross-platform identity (shared user ID across platforms)
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
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 |
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)
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).

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

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'
})

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

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.*

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).