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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Authentication tells a system which identity presented a credential; it does not decide whether that identity may perform a particular action on a particular resource right now. To stop an AI agent from taking unauthorized actions, enforce a separate authorization check at the trusted tool or service that will carry out the action—not in the model’s prompt or its final response.
What authentication proves—and what it does not
Authentication establishes a caller’s identity, such as an agent instance or a user acting through an agent. Authorization evaluates a request: whether that principal may perform this operation on this target, with these parameters, under the applicable conditions. A valid token can establish identity while the requested action is still out of bounds.
| Question | Security control | Example |
|---|---|---|
| Who presented the credential? | Authentication | Verify the token and identify the agent, user, or service. |
| May this principal perform this action on this target? | Authorization | Check whether the agent may send this message to this recipient using the delegated user’s rights. |
OWASP’s MCP07:2025 guidance calls for server-side token validation and permission evaluation on each request. A login, a broad session grant, or an agent’s claim that an action is allowed is not a substitute for that decision.
Why a properly authenticated agent can still cause harm
Agents often read material that was not written as trusted instructions: email, documents, web pages, or other retrieved content. NIST’s CAISI discussion, Strengthening AI Agent Hijacking Evaluations (January 2025), describes indirect prompt injection, in which malicious instructions embedded in ordinary-looking content influence an agent. In the scenarios CAISI tested, agents were frequently induced to follow instructions involving code execution, data exfiltration, or phishing. That is a qualitative finding about those tested systems and scenarios, not a universal success rate for agents.
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If the resulting change in an agent’s behavior can reach tools backed by broad permissions, a manipulation of text can become a real-world side effect. OWASP’s LLM06:2025 Excessive Agency guidance identifies excessive functionality, permissions, and autonomy as distinct contributors to this risk. Prompt defenses can help, but the model must not be the final authority on whether its own proposed action is permitted.
Where to enforce authorization
Place the decisive check in a trusted component that controls execution: the tool endpoint, an API gateway or policy service, an execution proxy, or the downstream application. The component that performs—or directly authorizes—the side effect should verify the request’s identity and authority. OWASP’s AI Agent Security Cheat Sheet states: “Enforce authorization in the execution component, outside the agent’s context.”
For each call, evaluate the agent identity, any user delegation, the requested operation, the target resource, the granted scope, and the relevant action parameters. Deny by default if identity, policy, or required approval cannot be validated. If the policy decision happens only when a user logs in or when a session begins, it may not reflect what the agent is trying to do now.
- Do not trust a user or agent identity asserted only in client-supplied metadata. Verify it through a trusted credential or token.
- Keep the authority context attributable across the human, agent instance, orchestrator, and tool endpoint. OWASP MCP07:2025 flags unverified caller identity and missing identity correlation in logs as risk indicators.
- Check authorization on every action-capable request, including requests made after retrieved content or a prior tool result changes the agent’s plan.
- Make policy failures fail closed: if the decision service is unavailable or cannot validate a required condition, do not execute the side effect.
Limit what each agent can do
Give an agent only the functions and permissions its task requires. Separate reading from writing, restrict which resources it can reach, and keep high-privilege operations in distinct workflows. An agent that reads email does not automatically need the ability to send or delete it. OWASP’s excessive-agency guidance recommends implementing only the necessary functionality and permissions and enforcing authorization in downstream systems.
Use the requesting user’s constrained authority where possible rather than routing every action through a generic privileged service account. Keep credentials short-lived, attributable, minimally scoped, and revocable; avoid shared, long-lived tokens. NIST’s Back to the Future: Why Agentic AI Needs a Strong Identity Foundation cautions that API keys provide broad, unscoped access and lack more granular authorization for how an agent interacts with a service. A shorter-lived credential reduces exposure time, but it still needs an appropriate scope and a per-action policy check.
Make human approval specific to the action
Approval should match the impact of the operation. A read-only lookup that is already within the agent’s authorized scope may not need an interactive prompt. Sending an external message, deleting data, changing privileges, moving money, or deploying to production warrants stronger controls.
When approval is required, show the person the actual operation and bind their decision to the exact tool call, target, and normalized parameters. The trusted executor should validate that approval immediately before acting. If a recipient, amount, resource, or other meaningful parameter changes, require a fresh decision. For critical or irreversible actions, consider step-up authentication and replay protection. Repeated vague approval prompts can lead to consent fatigue, so reserve friction for meaningful risk rather than asking for confirmation on every low-risk step.
Compare designs by the boundary they enforce
| Design choice | Weaker approach | Stronger approach | Why it matters |
|---|---|---|---|
| Enforcement point | Rely on the model or prompt to refuse unsafe requests. | Check policy in the tool, gateway, execution proxy, or downstream service. | The check remains outside the agent’s control when its plan is manipulated or mistaken. |
| Credential design | Use a broad, static, shared credential. | Use attributable, revocable credentials with narrow scope and limited lifetime. | Limits the authority and exposure associated with a compromised or misused credential. |
| Delegation | Run actions through a generic privileged service identity. | Constrain actions to the requesting user’s authorized context where possible. | Prevents the agent from inheriting unrelated service-level privileges. |
| Approval | Ask for a vague “allow” without binding approval to the request details. | Use risk-based review of the exact action and parameters. | A changed request cannot silently reuse an approval for a different action. |
| Evidence of security | Count a reassuring final response or refusal as proof. | Test execution-time blocks and retain logs of decisions and outcomes. | Shows whether unauthorized side effects were actually stopped. |
Build an audit trail and test the execution boundary
Log enough context to reconstruct what happened: the human and agent identities, delegation and scope, requested operation, target, policy decision, approval if applicable, and outcome. Correlate those records across the orchestrator and tool endpoint without treating client-provided identity labels as proof.
Best Value
Test whether the executor blocks a call when identity, scope, target, or required approval is invalid—not merely whether the model says it will refuse. Include indirect-injection scenarios involving untrusted email, files, or websites, and check whether an agent can reach an out-of-scope action after its plan changes. NIST CAISI recommends adaptive, task-specific evaluations and notes that testing across multiple attempts can better reflect risk. A useful test result is evidence that the protected side effect did not occur, accompanied by the authorization decision and execution record.
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