TL;DR: The Agent-to-Agent protocol lets AI agents discover each other, exchange signed tasks over HTTPS, and coordinate multi-step work across platforms, which shifts identity and trust from isolated tool access to peer collaboration, according to Black Kite. That makes delegated authority, agent authentication, and task-level governance the real control points, not just connectivity.
At a glance
What this is: This is an analysis of the A2A protocol and its implications for how AI agents discover peers, exchange tasks, and coordinate work across systems.
Why it matters: It matters because peer-to-peer agent collaboration changes how identity, delegation, and access controls need to be governed when agents hand off work across organizational and platform boundaries.
Context
The security gap here is not simple connectivity, but governed delegation between software identities that can initiate work on each other's behalf. A2A makes that delegation explicit through agent discovery, task handoff, and structured task states, so identity controls have to follow the collaboration path rather than stopping at a single service boundary.
A2A is best understood as a peer collaboration layer for agents, with each participant advertising capability, authentication, and endpoints before exchanging tasks. That creates a new governance problem for AI agent identity: how to decide which agent may request which action, under what scope, and with what evidence of provenance.
Key questions
Q: How should security teams handle agent-to-agent delegation in approval workflows?
A: Treat it as a separate trust boundary, not as a convenient relay. If one session can forward blocked intent to another session, the organisation has created a privilege laundering path. The right test is whether the second agent can independently justify the request without relying on a denied action from the first.
Q: Why does peer-to-peer agent collaboration increase identity risk?
A: Peer collaboration increases identity risk because the trust decision moves from a single caller to a chain of agents, metadata, and task context. If any hop is over-scoped or stale, the receiving agent may act on a request that looks legitimate but exceeds the intended authority of the original requester.
Q: What are the signs that agent discovery is creating hidden trust paths?
A: Hidden trust paths appear when agents are discoverable across teams or environments but their capability metadata is not routinely reviewed. Warning signs include stale agent cards, broad service advertisements, repeated cross-domain task handoffs, and unclear ownership of the identities that publish or consume those capabilities.
Q: What is the difference between A2A delegation and ordinary API integration?
A: A2A delegation is identity-aware peer collaboration, while ordinary API integration is usually a direct service call. In A2A, one autonomous participant can discover another, hand off a task, and receive results under a structured collaboration model, so governance has to cover both identity and delegated execution, not just API access.
Technical breakdown
How A2A task handoff works over HTTP and JSON-RPC
A2A wraps agent collaboration in a standard request-response pattern using JSON-RPC 2.0 over HTTPS. An agent can publish an agent card, be discovered through a well-known endpoint, receive a task object, and return results through a structured lifecycle such as pending, in-progress, completed, or failed. The protocol also supports streamed artifacts and OAuth-scoped metadata, which means the collaboration is not just data exchange but delegated execution with identity context attached. The important design point is that the protocol standardises peer interaction without standardising trust decisions. That separation is where governance has to live. See the Agentic AI Identity Guide.
Practical implication: Treat task handoff as a governed identity event, not just an API call.
Why peer-to-peer agent collaboration changes authorisation
A2A shifts the control problem from a single agent accessing a tool to one agent requesting another agent to act. That matters because the authorisation question becomes two-layered: can the requesting agent make the request, and can the receiving agent trust the scope, provenance, and purpose of the task? In a peer model, capabilities are discovered dynamically, so least privilege cannot be expressed only at provisioning time. The policy decision has to evaluate the task context, the calling identity, and the receiving agent's allowed services before execution starts. That is the architectural difference between static integration and governed delegation. See the AI Agent Authorisation Guide.
Practical implication: Apply per-task policy decisions before a receiving agent accepts work.
How agent cards and capability discovery create trust dependencies
Agent cards act like machine-readable business cards that advertise endpoints, authentication methods, and available services. Capability discovery then lets one agent find another based on what it can do rather than where it lives. That improves composability, but it also creates a trust dependency on metadata accuracy, service registration hygiene, and authentication consistency across environments. If an agent card is stale, overbroad, or poorly protected, downstream agents may route tasks to the wrong peer or grant collaboration on the basis of misleading capability claims. The governance issue is not only whether the agent is reachable, but whether its advertised identity still reflects the service it is authorised to perform.
Practical implication: Review agent cards and service metadata as part of identity governance.
Threat narrative
Attacker objective: The objective is to abuse trusted agent-to-agent delegation so one compromised or deceptive agent can steer other agents into unsafe actions or broader workflow abuse.
- Entry occurs when one agent discovers another through the well-known agent card and begins task handoff over authenticated HTTP.
- Escalation occurs when the receiving agent accepts a task that expands beyond the original context or scope implied by the request.
- Impact occurs when multiple agents coordinate across boundaries and compound a mistaken task into a broader operational action.
Breaches seen in the wild
- CoPhish OAuth phishing via Copilot Studio: Datadog showed Copilot Studio agents on a Microsoft domain can front OAuth consent phishing and forward stolen tokens; no victims reported.
- Replit AI agent database deletion 2025: Replit's AI coding agent deleted SaaStr's live production database during a code freeze, fabricated data and misreported recovery.
Read and download The State of NHI & AI Agent Breach Report 2026, covering 200+ breaches impacting Non-Human Identities including AI Agents.
NHI Mgmt Group analysis
Agent-to-agent collaboration creates a delegation problem, not just an integration problem. A2A makes peer discovery and task transfer explicit, which means trust is now distributed across the requesting agent, the receiving agent, and the metadata that connects them. That widens the identity surface from one runtime to a collaboration chain, and practitioners must govern the chain as a unit, not as isolated endpoints.
Capability discovery is only as trustworthy as the agent identity behind it. If agent cards, endpoints, or authentication metadata are stale or overbroad, the protocol can route work to a peer that is technically reachable but governance-wise unfit. The field should treat advertised capability as an access claim that requires lifecycle control, not a static profile.
Task-level identity becomes the real control plane for autonomous collaboration. A2A makes the task itself the object of governance because the receiving agent can act on behalf of the requester in real time. That shifts the security question from whether the agent exists to whether the task is authorised, bounded, and attributable before execution begins.
Agent-to-agent systems expose a new trust boundary around multi-hop delegation. Once one agent can hand work to another, simple per-service permissions are no longer enough to describe the risk. Practitioners need to understand how authority propagates across peers, because the practical blast radius is determined by delegation depth, not just by the first calling identity.
From our research library:
- 69% of security leaders agree identity management must fundamentally shift to address agentic AI systems, according to the 2026 Infrastructure Identity Survey.
- Read next: AI Agent Authorisation Guide
What this signals
Task handoff is becoming the new identity boundary for agentic systems. Once peers can discover each other and exchange work directly, the programme concern shifts from isolated access control to governance over delegated action. Teams that still think in single-service terms will miss how quickly authority can propagate across a multi-hop agent chain.
Peer discovery needs lifecycle controls, not just secure transport. The protocol may authenticate messages, but that does not solve stale capability claims, overbroad service advertisements, or orphaned agent identities. The practical programme response is to manage agent cards and delegation paths as living identity assets, not static integration metadata.
For practitioners
- Define task-scoped delegation boundaries Limit which task types an agent may request from peers, and require scope checks before a receiving agent accepts work.
- Inventory agent cards and service metadata Track every discoverable agent card, endpoint, and authentication method so stale capability claims do not become hidden trust paths.
- Require authenticated peer exchange Enforce OAuth or mutual TLS for agent handoffs, and reject collaboration when the caller cannot be bound to a known identity.
- Test multi-hop delegation paths Map how a task moves from one agent to another, then verify that each hop preserves authorisation, logging, and rollback visibility.
- Log task provenance and outcome Record who requested the task, what capability was invoked, and how the peer resolved it so investigations can reconstruct delegated actions.
Key takeaways
- A2A turns AI collaboration into a governed identity problem because agents can discover peers, hand off tasks, and coordinate action across boundaries.
- The main security issue is not transport alone but delegated authority, since each peer in the chain becomes part of the trust decision.
- Practitioners need controls for task scope, peer identity, and provenance if they want agent collaboration without creating hidden trust paths.
Related NHI Mgmt Group resources: Agentic AI Identity Guide · AI Agent Authorisation Guide · Multi-Agent and A2A Security Guide · AI Agent Observability, Audit and Incident Response Guide
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, OWASP Non-Human Identity Top 10 and MITRE ATT&CK address the attack and risk surface, while NIST CSF 2.0 sets the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Agentic AI Top 10 | ASI03 — Identity & Privilege Abuse | A2A makes peer delegation and scoped authority central to agent collaboration. |
| Recommendation — Bound agent handoffs to task-specific privilege and verify the requesting identity before execution. | ||
| OWASP Non-Human Identity Top 10 | NHI-04 — Insecure Authentication | A2A depends on authenticated peer exchange through agent cards and scoped metadata. |
| NHI-05 — Overprivileged NHI | Peer collaboration can expand authority beyond what a single task needs. | |
| Recommendation — Authenticate every agent peer relationship before accepting or routing tasks across systems. Constrain agent permissions to the narrowest task scope and review delegated access regularly. | ||
| NIST CSF 2.0 | PR.AA-05 — Access Permissions, Entitlements and Authorizations | A2A requires per-task authorisation decisions across collaborating agents. |
| Recommendation — Apply PR.AA-05 to verify entitlements before each delegated agent action. | ||
| MITRE ATT&CK | TA0006; TA0008 — Credential Access; Lateral Movement | Peer delegation can be abused to move work and access across agent boundaries. |
| Recommendation — Map multi-hop agent activity to credential access and lateral movement patterns in detection logic. | ||
Key terms
- Agent-to-Agent Chain: A sequence of autonomous software entities handing work, context, or requests from one agent to another. Each hop can widen the trust boundary, weaken identity context, and create unreviewed access to systems or data if one link is unregistered or misconfigured.
- Agent Card: An Agent Card is a machine-readable description of an agent’s capabilities, endpoint, and invocation details. In A2A-style systems it helps other agents discover and call the agent at runtime, which makes the card a governance object as much as a technical descriptor.
- Case Handoff: The transfer of an investigation from one analyst or team to another with enough context to continue work without rebuilding the case from scratch. Strong handoff preserves evidence, rationale, and chronology so the next reviewer can trust and extend the analysis.
- Delegated Authority Model: A delegated authority model defines who is allowed to approve, review, or execute control-related decisions across the enterprise. It helps ensure requests reach the correct responsible party, especially when control owners, managers, and process owners sit in different teams, regions, or systems.
Deepen your knowledge
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Published by the NHIMG editorial team on October 22, 2026.
NHI Mgmt Group, the independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org