Agent-to-Agent Authentication: How One Agent Verifies Another at the API Boundary
Multi-agent systems route work between agents that authenticate to one another. The pattern that worked for service-to-service traffic (mTLS plus a shared service account) under-attributes the action. Agent-to-agent authentication needs the workload identity of the calling agent plus the delegation chain back to the natural person, plus per-call records that capture the chain. This piece walks through the three properties an agent-to-agent auth model must support, the token-exchange pattern that satisfies them, and where the policy decision lands.