Trust Scoring and Identity Verification for Autonomous AI Agent Payment Transactions

This document specifies a protocol for trust scoring, identity verification, and spend limit enforcement for autonomous AI agents that initiate financial transactions. As AI agents gain the capability to make payments via protocols such as the Machine Payments Protocol (MPP), a standardised mechanism is needed to verify agent identity, assess trustworthiness, and enforce financial limits based on behavioural history. The protocol defines a five-dimension trust scoring model, per- agent cryptographic identity using ECDSA P-256 key pairs, challenge-response identity verification, spend limit tiers derived from trust scores, anomaly detection for financial behaviour, and a public trust query API for third-party platforms. This specification complements draft-sharif-mcps-secure-mcp, which provides message-level cryptographic security for the Model Context Protocol (MCP). Together, the two specifications address protocol security (MCPS) and financial trust (this document) for the AI agent economy.