Transaction Trust Scoring for Agent Commerce: Infrastructure for Verifiable Agent-to-Vendor Transactions

As autonomous AI agents begin executing financial transactions on behalf of human principals, the trust problem shifts from identity to transaction-level risk. We present the Transaction Trust Score (TTS), a real-time scoring system that aggregates four independent signals—entity verification, constraint compliance history, behavioral fingerprinting, and counterparty risk assessment—into a single trust verdict delivered in under 200ms. TTS is formalized as the Delegated Agent Commerce Protocol (DACP), a Protocol Buffer schema published on the Buf Schema Registry. We implement TTS as a Cloudflare Workers service integrated with Helix Fabric for entity verification and demonstrate differentiated scoring across verified and synthetic entities.