Give it a site URL and get back a complete GA4 measurement plan — which events to track, what parameters each carries, which custom dimensions to register, and which events to mark as key events. The deliverable is a spec a developer or GTM builder can implement directly. No account connection required.
It pairs with /gtm-tracking-plan, which turns this plan into the actual GTM tags,
triggers, and variables.
Usage
/ga4-measurement-plan example.com — measurement plan for the site
/ga4-measurement-plan example.com "drive demo bookings" — bias the plan toward a goal
Steps
1. Understand the site
WebFetch the URL and a representative spread of pages (home, product/category,
pricing, signup/checkout, contact). Determine:
- Site type — ecommerce, lead gen, SaaS, content/media, marketplace
- The primary conversion and any secondary conversions (newsletter, demo, account creation)
- The funnel steps a visitor passes through to convert
- Notable interactions worth measuring (search, filters, video, downloads, configs)
If a business goal was passed as an argument, make the plan serve it first.
2. Start from what GA4 already gives you
Note which events come free and need no implementation:
- Automatically collected:
first_visit,session_start,page_view,user_engagement - Enhanced Measurement (if enabled):
scroll,click(outbound),view_search_results,video_*,file_download,form_start,form_submit
Flag any of these the team should rely on rather than rebuild.
3. Recommended events for the site type
Map the site to GA4's recommended events — using the recommended names matters because GA4 builds reporting around them:
- Ecommerce:
view_item_list,view_item,select_item,add_to_cart,view_cart,begin_checkout,add_shipping_info,add_payment_info,purchase,refund - Lead gen / SaaS:
generate_lead,sign_up,login,search, plus custom events for the funnel - Content / media:
search,select_content,share,join_group
For each: when it fires and its parameters (e.g. purchase → transaction_id,
value, currency, items[]).
4. Custom events for everything else
For interactions GA4 has no recommended event for, design custom events following the
rules: snake_case, ≤40 characters, descriptive, no reserved prefixes
(google_, firebase_, ga_), lowercase. Examples: demo_requested,
pricing_plan_selected, quote_calculated.
Keep the taxonomy tight — a parameter on a shared event usually beats a brand-new
event (cta_click with a cta_location parameter, not ten separate click events).
5. The event taxonomy table
Produce the core deliverable — one row per event:
| Event name | Type | Fires when | Parameters | Key event? |
|---|---|---|---|---|
purchase |
recommended | order confirmation page loads | transaction_id, value, currency, items[] |
✅ |
generate_lead |
recommended | contact form submitted | form_id, lead_source, value |
✅ |
demo_requested |
custom | demo form submitted | plan_interest |
✅ |
| ... |
6. Custom dimensions & metrics to register
Event parameters are invisible in standard GA4 reports until registered as custom dimensions. List every non-standard parameter from Step 5 that needs registering:
| Parameter | Scope | Register as | Why |
|---|---|---|---|
lead_source |
event | custom dimension | segment leads by origin |
plan_interest |
event | custom dimension | see which plan drives demos |
Warn against high-cardinality parameters (IDs, timestamps) as dimensions, and note the 50 event-scoped / 25 user-scoped limits.
7. Key events (conversions)
Recommend which events to mark as key events. Be selective — 3–8 is healthy. Mark
real business outcomes, never page_view or scroll. Note which key events should
also be imported into Google Ads for bidding.
8. Output
Deliver as one document:
GA4 Measurement Plan — [site]
Site type: ... | Primary conversion: ...
1. Already covered (automatic + Enhanced Measurement): ...
2. Event taxonomy table (recommended + custom)
3. Custom dimensions & metrics to register
4. Key events to mark as conversions (and which to send to Google Ads)
5. dataLayer payload examples for the 3-5 most important events
6. Implementation notes & sequencing
End with the handoff line: "Run /gtm-tracking-plan [url] to turn this into GTM
tags, triggers, and variables."
Critical rules
- Use GA4's recommended event names wherever one exists — reporting depends on them.
- A registered parameter beats a new event. Keep the taxonomy small.
- Custom events must follow the naming rules —
snake_case, ≤40 chars, no reserved prefixes. - Never recommend collecting PII (email, phone, name) in events or parameters — it violates Google policy.
- This produces a plan. To audit a live GA4 property, use
/ga4-audit(requires Cogny MCP).