Commercial General Liability (CGL) is the foundation of any subcontractor's insurance. It responds to third-party claims, a passerby injured by falling debris, a homeowner's flooring ruined by a plumbing mistake, including the legal costs of defending those claims.
Most GC contracts set a minimum CGL limit, commonly $1M per occurrence and $2M aggregate, and require the GC to be added as an additional insured. It is the single most important coverage to verify on every COI.