The rapid proliferation of AI agents in 2025-2026 has created a fundamental trust problem: platforms cannot distinguish legitimate agents from malicious actors, leading to blanket blocking or expensive bot detection, while agents cannot prove their legitimacy, resulting in unreliable access and legal disputes. Trust Signals for Agentic Interactions (TSAI) addresses this challenge through an open, standards-based protocol that enables agents to present verifiable credentials issued by independent Trust Authorities and verified by platforms. Built on W3C Verifiable Credentials and Decentralized Identifiers, TSAI provides cryptographically signed credentials containing multi- dimensional trust signals—including verified operator identity, behavioral reputation, economic stake, and authorized constraints—while preserving user privacy through zero personally identifiable information in credentials.

TSAI employs a four-tier trust model (T0-T3) that balances performance and security across diverse risk levels. Lower tiers (T0-T1) provide basic identity and reputation signals with offline verification under 5 milliseconds, serving 95% of agent traffic including browsing, search, and public API access. Higher tiers (T2-T3) add economic accountability through posted collateral and insurance, plus fine-grained authorization constraints, with challenge-response verification and real-time Trust Authority queries for high-value transactions and regulated operations. This tiered approach enables incremental adoption—starting with simple identity verification and progressively adding reputation, economic stake, and constraints as the ecosystem matures—while optimizing for the common case of low-risk, high-volume interactions.

The protocol operates through a three-party model where professional Trust Authorities evaluate agents and issue short-lived credentials, agents present these credentials when accessing services, and platforms verify authenticity and make risk-calibrated access decisions based on their own policies. TSAI explicitly signals rather than enforces: the protocol defines what trust signals exist and what they mean, but platforms retain full autonomy in interpreting signals and setting access policies. With governance transferring to the Linux Foundation and early adoption from major European retailers representing over €80 billion in annual gross merchandise value, TSAI provides the trust infrastructure necessary for agentic commerce to scale while maintaining accountability, transparency, and interoperability across the emerging agent ecosystem.

IMPORTANT: This is still a confidential cross-industry project under the leadership of AWS. Please do not publish on the website before discussing with me. Thanks!