Responsibility is about the bidder, not the bid. A contracting officer must affirmatively determine a prospective contractor is responsible before award, weighing things like adequate finances and the ability to meet the schedule. A low number from a firm that cannot demonstrate capacity can still be passed over.
Federal standards spell out the elements: adequate financial resources, the ability to meet the schedule, a satisfactory performance and integrity record, the necessary organization and equipment, and eligibility to receive an award. On public works, a contractor found nonresponsible can usually contest the determination. That is one reason agencies document their reasoning carefully rather than rejecting a low bidder on a hunch. Most of these criteria live in the bid documents and the firm's qualification record. Nonlinear's pursuit screening reads a solicitation and surfaces the responsibility hurdles (licensing, bonding capacity, experience requirements) early enough that you can confirm you clear the bar before sinking hours into an estimate.
