Agent skill
instrumentation-planning
Plan what to measure in web applications. Use when starting observability or prioritizing instrumentation.
Install this agent skill to your Project
npx add-skill https://github.com/nexus-labs-automation/web-observability/tree/main/skills/instrumentation-planning
SKILL.md
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.methodnotmethodhttp.request.durationnotapiCallTimeurl.pathnotpage
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 implementationskills/error-tracking- Tier 1 implementationskills/source-map-setup- Tier 1 implementation
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