Scenarios target real confusion clusters in Epic's UE 5.8 catalog
(StaticMesh vs SkeletalMesh set_material, three tag systems, CurveTable
vs DataTable rows, Niagara Component vs System variables, four capture
variants, zero-keyword phrasing). Mocks return realistic editor errors
on wrong-type calls; scoring is strict (clean solve = correct tool with
zero distractor calls; first-call accuracy tracked separately).
Key result: first-call selection is unreliable in EVERY mode — eager
with all 199K of schemas in context managed 2/10 — but clean solves stay
75-95% because agents probe (get_components, get_material_slots) before
committing. The probe loop works through the 3-tool bridge at 1/4 the
cost of eager ($1.60-1.69 vs $6.49/task, Opus 4.8). On Haiku the
listing beats bare bridge 18/20 vs 15/20 (core-tool substitution again).
Zero distractor invocations across all 50 Opus runs.
