A coordination layer that lets one agent communicate, plan, and execute with other agents. The security challenge is not only what each agent can do, but how authority, context, and accountability move across the chain during delegation.
Expanded Definition
Agent2Agent Protocol describes the coordination rules that let one autonomous agent pass intent, context, or execution requests to another agent. In NHI security, the critical issue is not simply inter-agent messaging, but whether authority is delegated, constrained, logged, and reversible across each handoff. The term is still evolving in industry usage, so definitions vary across vendors and implementations, especially where agent routing overlaps with workflow orchestration or tool invocation. Practitioners should treat it as a security boundary problem as much as a communication layer.
This matters because an agent chain can amplify privilege if the receiving agent inherits too much trust from the sender. That makes the protocol relevant to identity propagation, scoped delegation, and auditability under models such as the OWASP Top 10 for Agentic Applications 2026 and the NIST AI Risk Management Framework. The most common misapplication is assuming an agent-to-agent exchange is safe because each agent was individually authorised, which occurs when delegation rules are not revalidated at every hop.
Examples and Use Cases
Implementing Agent2Agent Protocol rigorously often introduces coordination overhead, requiring organisations to weigh autonomy gains against tighter policy enforcement and more detailed logging.
- A procurement agent asks a finance agent to validate payment timing, but the receiving agent only gets a read-only context token instead of broad account access.
- An incident-response agent forwards a containment task to a remediation agent, while preserving an immutable chain of custody for every instruction and decision.
- A customer-support agent delegates a case lookup to a billing agent, with the protocol constraining which fields and actions can be shared.
- An engineering agent routes a build approval request to a deployment agent, but tool access is re-scoped for that specific transaction rather than inherited permanently.
- Security teams map agent handoffs against the patterns discussed in OWASP NHI Top 10 and compare them with the MITRE ATLAS adversarial AI threat matrix when evaluating how an attacker could steer delegation.
These examples show why the protocol is useful for multi-agent orchestration, but only when policy is attached to the message flow, not just the endpoint identity.
Why It Matters in NHI Security
Agent2Agent Protocol becomes a governance issue whenever one compromised agent can influence others. Without explicit controls, an attacker can pivot from a low-risk agent into higher-value systems by abusing delegated context, replaying instructions, or inducing an overly trusted downstream agent to execute unsafe tool calls. That creates a classic NHI failure mode: authority moves faster than human oversight. NHI Management Group research shows that 97% of NHIs carry excessive privileges, increasing unauthorised access and broadening the attack surface, which is exactly the condition that makes inter-agent delegation dangerous when privilege boundaries are vague.
Operationally, this term sits at the intersection of identity lifecycle, least privilege, and audit integrity. The problem is not abstract: the Ultimate Guide to NHIs reports that only 5.7% of organisations have full visibility into their service accounts, which is a warning sign for any environment where agents are allowed to coordinate and delegate on behalf of each other. The same visibility gap can hide unauthorized agent chains, unrevoked tokens, and unexplained tool use. Organisaties typically encounter the real risk only after a delegated action creates an outage, data exposure, or unauthorized transaction, at which point Agent2Agent Protocol becomes operationally unavoidable to address.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Agentic AI Top 10 and CSA MAESTRO address the attack and risk surface, while NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Agentic AI Top 10 | A2A-01 | Agent-to-agent delegation is a core agentic-app security concern. |
| NIST AI RMF | AI RMF addresses governance, transparency, and accountability for agentic systems. | |
| CSA MAESTRO | MAESTRO models multi-agent trust, orchestration, and threat boundaries. |
Map agent delegation to risk controls, provenance, and human oversight requirements.
