The article argues that current AI agent development focuses too heavily on the "visible stack"—models, prompts, and tool connectivity—while neglecting the critical "contract stack" required for reliable agency. The author distinguishes between "reach" (the ability to access tools) and "agency" (the authorized ability to make binding decisions under specific conditions). To move from impressive demos to production-ready systems, developers must shift from simply connecting APIs via Model Context Protocol (MCP) to engineering rigorous boundaries. This involves designing a "control loop" where planning, tool selection, and memory are explicit and inspectable rather than hidden within long natural-language instructions. Key technical recommendations include treating tools as formal contracts with defined parameters, error states, and mutation permissions, rather than mere plumbing. Furthermore, "skills" should be packaged as operational knowledge containing specific triggers and failure modes, and "memory" should be treated as governed state—prioritizing organized, expiring information over voluminous, unmanaged chat transcripts. Ultimately, the author posits that an agent's reliability is determined by the harness—the set of boundaries and evaluation metrics that dictate how an agent handles failure, escalation, and state changes.