instrumentation-planning

name	instrumentation-planning
description	Plan what to measure in web applications. Use when starting observability or prioritizing instrumentation.
triggers	["planning telemetry","prioritize instrumentation","what should I track"]
priority	1

Instrumentation Planning

Strategic guidance for what to measure in web applications.

Core Question

For each user job, ask:

• Did it complete? → completion rate
• How long? → duration (p50, p95, p99)
• What failed? → error type, context
• Did they give up? → drop-off rate
• How smooth? → Core Web Vitals, friction signals

Priority Tiers

Tier	Focus	Priority
1	Errors + source maps	P0 - Day 1
2	Core Web Vitals	P0 - Day 1
3	User context + breadcrumbs	P0 - Week 1
4	Route transitions + API tracing	P1 - Week 2
5	Business metrics + synthetic tests	P2 - Month 1

Core Web Vitals Thresholds

Metric	Good	Needs Improvement	Poor
LCP	≤2.5s	≤4.0s	>4.0s
INP	≤200ms	≤500ms	>500ms
CLS	≤0.1	≤0.25	>0.25

OTel-Compatible Naming

Use now for easier migration later:

• http.request.method not method
• http.request.duration not apiCallTime
• url.path not page

Anti-Patterns

See references/anti-patterns.md for:

• Measuring everything (noise, bundle bloat)
• Skipping source maps
• Blocking main thread
• PII in breadcrumbs

Implementation Details

See references/instrumentation-patterns.md for:

• Detailed 5-tier checklist
• Span naming conventions
• Sampling strategies

See references/jtbd.md for Jobs-to-be-Done framework.

Related Skills

• skills/core-web-vitals - Tier 2 implementation
• skills/error-tracking - Tier 1 implementation
• skills/source-map-setup - Tier 1 implementation