What is Signal Health Score (AI Max)?

The Signal Health Score is a single number summarizing whether an account's conversion data is trustworthy enough to train Google's AI bidding — combining attribution drift, signal composition, and training-data pollution.

Why it matters

AI Max and Smart Bidding learn from whatever conversion data they are fed. If that data is heavily modeled or drifting from GA4 reality, the algorithm learns confidently from fiction — and CPA rises while the system reports that it is "learning".

How ClickCatalyst detects it

The score combines the attribution drift between Ads and GA4, the composition of conversion signals (click, view-through, cross-device, modeled), and the modeled percentage per campaign (training-data pollution).

It also stages each campaign in the algorithm learning lifecycle and computes a Machine vs Human Trust Score — the definitive CPA comparison between AI-expanded traffic and manually controlled traffic for this specific account.

Inputs: attribution_drift · signal_composition · modeled_pct
Output: Signal Health Score + per-campaign maturity stage
        + Machine vs Human CPA trust comparison

Example

An account where Smart Bidding "is learning but CPA keeps rising" typically shows a low Signal Health Score: high modeled share plus drift means the algorithm is optimizing toward phantom conversions.