ga4-measurement-plan

name	ga4-measurement-plan
description	Build a GA4 measurement plan from a site URL — event taxonomy, parameters, custom dimensions, and key events to mark as conversions
version	1.0.0
author	Cogny AI
platforms	[]
user-invocable	true
argument-hint	<site url> [business goal]
allowed-tools	["WebFetch","WebSearch","Bash","Read","Write"]

GA4 Measurement Plan

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

1. Use GA4's recommended event names wherever one exists — reporting depends on them.
2. A registered parameter beats a new event. Keep the taxonomy small.
3. Custom events must follow the naming rules — snake_case, ≤40 chars, no reserved prefixes.
4. Never recommend collecting PII (email, phone, name) in events or parameters — it violates Google policy.
5. This produces a plan. To audit a live GA4 property, use /ga4-audit (requires Cogny MCP).