Systematic per-perimeter assessment protocol. Measure: schema coherence, corroboration count, parametric recall rate, attribution rate, citation coverage, schema entropy rate. Output: verdict per perimeter (Defended/Contested/Undefended). Use for: engagement qualification, SOW scoping, bottleneck identification. Most common pattern: Defended identity, Contested domain, Undefended vocabulary. Diagnostic identifies weakest perimeter (constraining factor). Run pre-engagement and quarterly thereafter. Posture diagnostics replace “brand health” with mechanistic measurement. Critical sales tool — makes invisible problem visible.