Diagnose a Google Ads CPA spike fast
The Google CPA-spike sequence: conversions first, then mix shifts, then auction, then bid changes.
IntentWhy Google CPA jumped: measurement, mix, competition or bids.
- 4
- Steps
- 5
- Tools
- 2
- Rules
- 1
- Failure modes
When to use it
Use it when
- CPA jumped beyond noise on meaningful spend.
Do not use it when
- Windows inside conversion lag: wait it out or say so.
What it needs first
Required
Preconditions
- The account is ticked in the dashboard, confirmed via list_accounts.
Inputs
window- Analysis window.Default: last 30 days.
Procedure
In order. Every tool named is one the gateway ships, and links to its reference.
Split the spike: spend up, conversions down, or both.
Check conversion actions for measurement moves.
Check mix: did spend shift toward expensive campaigns or terms.
Check bid strategy and target changes.
Decision rules
The observable condition, what it lets you conclude, and what takes the conclusion back.
When
Conversions fell while clicks held
Conclude
Measurement or site first: route to tracking-audit before touching bids.
When
A target change predates the spike
Conclude
The strategy obeys its new number: the spike is the setting, working.
Evidence every conclusion must carry
- Every figure carries its account, metric and window.
- Anything below a readable sample size is reported as unjudged, not as zero.
Where the agent stops
- The readout changes nothing. Any change it motivates goes through Safe Writes: preview, human confirmation, then apply.
How it goes wrong quietly
The cases where the analysis is wrong and still looks right. Read them before trusting a number.
- Attribution lag makes the last 72h spike artificially: trim before judging.
What the answer contains
- 01Readout
- The figures, with windows and accounts named.
- 02Flags
- What deserves a deeper skill or a human decision.