Because agents do not just consume data, they initiate actions through tools. If tool access is not tied to delegated identity and explicit scope, the agent can inherit broad permissions that are difficult to constrain after the fact. That turns access control into a runtime guess instead of a governable decision.
Why delegated identity has to be explicit
AI agents are not governed safely just because they are “allowed” to act. They need a delegated identity that says who or what they are acting for, what authority they inherit, and where that authority stops. Without that, the agent becomes a broad proxy for the user, which makes review, approval, revocation, and accountability far harder than traditional access control.
That is why delegation should be scoped to the task, not to the personality of the assistant. If the agent can reuse a human session, a general-purpose token, or a long-lived credential, the governance model collapses into implicit trust. The question is not whether the agent can technically reach the tool, but whether the delegation boundary is narrow enough to be defensible.
For identity and delegation mechanics, Agentic AI Identity Guide explains how agent identity, delegation, registration, and retirement fit together, and RFC 8693: OAuth 2.0 Token Exchange is a useful delegation model when an agent needs a constrained on-behalf-of path rather than a shared credential.
Why tool boundaries matter more than the model’s intent
A tool boundary is the practical control that separates “the agent may reason about this” from “the agent may execute this.” That distinction matters because most real failures happen at the action layer: sending mail, deleting records, changing infrastructure, moving funds, or calling downstream services. If every tool is reachable under the same broad authority, a single bad prompt, confused objective, or misrouted instruction can become a material action.
Good governance therefore treats tool access as a set of explicit permissions, not a convenience feature. A read-only summarizer, a change-request agent, and a release agent should not share the same tool scope just because they sit in the same workflow. The narrower the tool boundary, the easier it is to reason about blast radius, separation of duties, and escalation paths.
For a control-oriented view, AI Agent Authorisation Guide covers task-scoped access, per-action policy decisions, and human approval gates, while Zero Trust for AI Agents frames the same problem as verify, scope, and continuously enforce rather than assume trust once the agent starts running.
What changes when the boundary is not enforced
When delegated identity and tool scope are vague, the agent can inherit permissions that are broader than the task requires and keep them longer than intended. That creates a governance gap: the organisation may believe it approved a narrow action, while the runtime system actually allowed a much wider one. Over time, this also produces hidden privilege accumulation, weak auditability, and difficult offboarding because no one can clearly state what the agent was authorised to do.
At scale, the problem becomes less about one misconfigured agent and more about repeated overreach across many workflows. A small exception in one automation pattern can turn into a standing pattern of excessive agency, especially where teams copy a working setup without re-evaluating the delegated identity or tool list. Once that happens, incident response becomes slower because revocation has to be inferred from logs instead of enforced by design.
For failure patterns in practice, AI Agent Observability, Audit and Incident Response Guide is useful because it focuses on attribution, abnormal action signals, and kill-switch design, and Agentic AI Security Guide places tools and identity inside the wider agent threat model instead of treating them as separate implementation details.
Risk and Threat Considerations
Delegated identity and tool boundaries are attractive attack surfaces because they turn a reasoning system into an execution path. If an attacker can influence the agent’s inputs, capture a token, or persuade the agent to invoke a broader tool than intended, the result is often not data exposure alone but an authenticated action with real side effects.
Failure mechanism: the agent receives authority that is broader than the task, or the tool layer fails to enforce a per-action decision, so malicious or mistaken instructions can cross the intended boundary and trigger unauthorized operations.
Impact: the compromise is no longer limited to the model’s output quality, it can include data deletion, privilege misuse, unauthorised transactions, lateral movement through connected systems, and delayed recovery because the action was executed under apparently valid delegated authority.
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, CSA MAESTRO and OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST Zero Trust (SP 800-207) and NIST SP 800-53 Rev 5 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Agentic AI Top 10 | ASI03 — Identity & Privilege Abuse | Agent governance depends on constraining delegated identity and tool scope. |
| ASI02 — Tool Misuse | Tool boundaries are the control that prevents unsafe or unintended agent actions. | |
| ASI10 — Rogue Agents | Weak delegation and broad tool access can let agents act beyond approved intent. | |
| Recommendation — Enforce per-action authorization and least privilege for every agent tool call. Restrict tool access to the minimum required actions and verify each invocation. Bind agent identity to explicit scope and revoke unsanctioned capabilities quickly. | ||
| CSA MAESTRO | A — Autonomy | Agent autonomy must be bounded so delegated action stays governable. |
| Recommendation — Define autonomy limits and require approval for high-impact agent actions. | ||
| NIST Zero Trust (SP 800-207) | PR.AA-01 — Identity and Credential Management | Delegated identity must be explicit before an agent can be trusted to use tools. |
| PR.AA-05 — Identity Assertions are Protected, Validated, and Bound to the System | Tool calls need bound identity assertions to preserve accountable access decisions. | |
| Recommendation — Assign distinct identities and credentials for agents instead of reusing human sessions. Bind agent assertions to the requesting workload and validate them at each boundary. | ||
| NIST SP 800-53 Rev 5 | IA-9 — Service Identification and Authentication | Agents and tools often authenticate as non-human services, so service identity matters. |
| AC-6 — Least Privilege | Scoped tool access is the core control that limits damage from agent misuse. | |
| Recommendation — Use service-specific authentication for agent-to-tool access and avoid shared credentials. Limit each agent to the minimum permissions needed for its current task. | ||
| OWASP Non-Human Identity Top 10 | NHI-05 — Overprivileged NHI | Agent identities are non-human identities, and excessive privilege is a direct governance risk. |
| Recommendation — Reduce standing privilege and scope every agent credential to its exact use case. | ||
Practitioner Guidance
What to verify: Confirm that every agent has a named delegated identity, a bounded purpose, and a tool list that is smaller than the user’s full access. If you cannot explain why a specific tool is needed for this agent, treat that tool as out of scope.
Decision rule: If the agent can change state, require per-action authorisation and a revocation path that works independently of the model. If the action is high impact, do not let approval live only in the prompt or the workflow description.
Practitioner takeaway: The governance question is not whether an agent is trusted in general, it is whether each tool invocation can be tied to a specific delegated identity, a specific scope, and a specific accountability trail.
Related resources from NHI Mgmt Group
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Reviewed and updated by the NHIMG editorial team on October 11, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org