Endpoint Liability Ledger

Every API an agency ships carries an ongoing cost: auth drift, schema changes, rate-limit surprises, and now agent traffic that hits endpoints no human designed for. The Endpoint Liability Ledger is a simple inventory discipline: before a build closes, list each endpoint, who owns it, what breaks it, and what the agency charges to keep it alive. Endpoints that appear on the ledger without a matching line in the retainer are margin leaks. The framework separates three tiers: static integrations (document once, monitor rarely), active integrations (client CRM or payment rails, monitored monthly), and agent-facing endpoints (rate-limited, spend-capped, audited). Zuplo's gateway model, which enforces authentication and spend caps across both inbound agent traffic and outbound LLM calls, is the pattern for the third tier. Agencies that price the ledger explicitly convert maintenance from a complaint into a defensible retainer line.