Give an AI agent its own accountable identity and only the tools, data, operations and time needed for its defined task. Start with no access, allow specific actions on specific resources, keep read and write authority separate, use short-lived credentials, and require fresh human approval for irreversible or high-impact actions. Authorization must be enforced by the system executing each tool call—not inferred from the model’s plan or a permission label. Log activity, review access and revoke it when the agent is no longer needed. See Microsoft’s least-privilege guidance, the OWASP AI Agent Security Cheat Sheet and the OWASP AI Agent and MCP Security guideline.
What “least privilege” means for an AI agent
Least privilege is not a single role such as “analyst” or “developer.” It is a set of limits applied to an identified agent: which resources it can reach, which operations it can perform, which data it may handle and how long the authority lasts. A summarization agent may need to read documents in one approved collection and create a draft. It normally does not need shell access, secret files, outbound network access, repository pushes, deletion or permission administration.
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OWASP describes the related principle as least agency: give an agent only the autonomy, tools and access its task requires, for only as long as it needs them. This matters because an agent can be influenced by malicious or incorrect content, call a tool in an unexpected sequence, or turn a narrow instruction into a much broader action. A constrained executor limits the damage when the model is wrong or manipulated.
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Permissions should therefore be evaluated on six dimensions:
#1 Best Overall
| Dimension | Question to answer | Good default |
|---|---|---|
| Identity | Which principal is making the call, and who owns it? | A distinct identity for each agent or independently managed instance, with a named sponsor and technical owner. |
| Resource | Which tenant, workspace, repository, site, collection or records can it reach? | The smallest useful resource boundary; exclude unrelated projects and environments. |
| Operation | Can it read, create, update, export, delete or administer? | Allow only the operations required by the task; separate read, write and administrative actions. |
| Data | What sensitivity and fields may enter the agent’s context? | Approved data classes and fields only; keep secrets and unrelated personal data out. |
| Duration | How long does the grant or token remain usable? | Short-lived, narrowly scoped credentials and time-bounded elevation. |
| Control | What happens before a consequential action executes? | Fresh human approval plus an independent authorization check for high-impact or irreversible operations. |
Start with an accountable identity
Do not run routine agent activity under a developer’s personal account or a shared service identity that hides which agent acted. A separate principal makes attribution, revocation and access review possible. Give each agent—or each independently managed production instance—a distinct identity when the platform supports it. Keep development, test and production identities and credentials separate.
Record a business sponsor and a technical owner. The sponsor confirms that the agent’s purpose remains valid; the technical owner maintains its code, tools and credential configuration. Microsoft’s Entra Agent ID best practices recommend a unique identity per agent instance and named sponsor and owner. OWASP likewise recommends identities that can be attributed and revoked independently.
Write the purpose before granting access
Create a short scope statement that an administrator can test against every proposed permission. Include:
- The single business task and expected output.
- The sponsor, technical owner and operating environment.
- Approved data sources and sensitivity boundaries.
- Required tools and the exact operations each tool may perform.
- Explicit exclusions, such as production databases, secret stores, shell commands, external posting or role changes.
- When the identity should expire or be re-evaluated.
“Handle customer operations” is too broad. “Read tickets in the returns queue and create a draft response; do not send, close, export or delete tickets” is testable. Microsoft’s July 2026 guidance recommends documenting purpose, approved data, tool dependencies and environment while treating an agent as a first-class principal: Least privilege for AI agents: identity, access and tool binding.
Build a deny-first tool and resource policy
Begin with no tools and add only what the scope statement justifies. For every tool, specify its allowed operations and target resources. Keep the policy readable enough for an access reviewer to see whether a requested call is in bounds.
| Example agent task | Allow | Keep denied unless separately justified |
|---|---|---|
| Summarize an approved document collection | Read the named collection; create a draft summary in a designated workspace. | Shell, secret files, external network calls, repository push, deletion and permission changes. |
| Prepare a support-ticket draft | Read assigned tickets and approved knowledge articles; create a draft response. | Sending messages, closing tickets, exporting the queue, changing assignment or accessing unrelated customer records. |
| Prepare a deployment change | Read the specified build and change records; generate a proposed change for review. | Production deployment, credential changes, role changes, destructive migration and direct access to unrelated environments. |
The syntax for an allow/deny manifest differs by product, so treat OWASP’s illustrative policies as a design pattern rather than portable configuration. The important property is enforcement outside the model: a tool appearing in an agent’s interface does not grant permission, and a model’s classification of an action is not an authorization decision.
Authorize the exact call at execution time
When the agent requests a tool, the executor or a trusted authorization service should evaluate the authenticated principal, operation, target and current policy. The decision should be made again when the action executes, not only when the agent session starts.
A useful authorization record contains:
- The agent identity and, where applicable, the initiating user.
- The exact operation, such as
read,create-draft,sendordelete. - The target resource and relevant object identifier.
- The token scope, expiration and environment.
- Required approval state and the approver identity.
- The policy decision and reason for denial or approval.
Bind the tool call to the identity that actually initiated it. Microsoft states that applications should bind every tool call to the initiating identity, authorize the exact action and target, use narrowly scoped tokens and require fresh confirmation for high-impact actions. The guidance is available at Identity, Access, and Least Privilege. OWASP makes the same separation: the execution component must check authorization even when a human approval workflow exists.
Scope data, resources and time
Resource scope should be the smallest boundary that produces a useful result. Prefer one repository over an organization, one site or collection over an entire tenant, and an assigned record set over every customer record. Limit fields and sensitivity where the platform allows it; an agent that needs order status may not need payment details.
Operation scope matters as much as resource scope. A token that can update a document is broader than one that can create a draft in a separate workspace. Keep read and write paths distinct when practical, and place export, delete, role administration and credential management in separate, tightly controlled roles.
Rank #3
Use short-lived credentials and narrow token audiences. Avoid placing durable production secrets in prompts, configuration visible to the model or an agent-readable file system. Do not reuse a human’s password or refresh token. The exact credential mechanism depends on whether the agent is autonomous, acts for a signed-in user or runs inside a particular platform.
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Autonomous service operation
An unattended agent with no user context should use a service identity with only the required application permissions. Its policy should identify the service as the principal and define the resources and operations it may use. Avoid granting broad organization-wide application permissions merely because the agent might need them someday.
Interactive, user-delegated operation
An agent acting on behalf of a signed-in user has a different authority model. In Microsoft Entra, the documented pattern is the on-behalf-of flow so the user’s access policy and consent apply; delegated permissions are preferred when they are sufficient instead of application permissions. These are Microsoft Entra implementation instructions, not a universal recipe for every identity platform. Verify the target platform’s current flow, consent and token rules before deployment. See Best practices for Microsoft Entra Agent ID.
Credential protection in Microsoft Entra deployments
For production Entra agents, Microsoft recommends managed or federated identities or certificates over client secrets. Isolate credentials across unrelated blueprints and environments, and store certificate private keys in Key Vault or a hardware security module. These mechanisms are Azure-specific options; other platforms may use different workload-identity or key-management services.
Put consequential actions behind fresh approval
Classify actions by impact and reversibility rather than by the model’s confidence. A narrow read or draft operation may run under a reviewed standing policy. Actions that affect people, money, production systems or security boundaries need a new approval close to execution.
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|---|---|---|
| Read approved data | Allow when the resource, data class and purpose match policy. | Usually reversible and low impact, though sensitive data still needs appropriate scope. |
| Create a draft or proposal | Allow in a designated workspace; require review before publication. | Separates preparation from an external or durable effect. |
| Send an external message | Require fresh human confirmation and executor-side authorization. | Creates an external commitment and may disclose information. |
| Delete or export data | Require fresh approval, narrow target selection and an auditable record. | May be irreversible or create a new disclosure path. |
| Purchase or move funds | Require an authorized approver and independent transaction checks. | Financial impact cannot be safely inferred from a model plan. |
| Deploy code or change production | Require change approval, environment checks and executor authorization. | Can affect availability, integrity and security at scale. |
| Change roles or permissions | Keep outside routine agent roles; require privileged approval and exact-target checks. | Changes the security boundary itself. |
Approval is an additional control, not a substitute for authorization. A user clicking “approve” does not permit an agent identity to act on a different target or use an unapproved operation. Microsoft and OWASP both require the executor to verify the exact action even after approval.
Defend against untrusted instructions and tool misuse
Agents routinely read webpages, documents, issue comments, emails and tool descriptions. Those sources can contain instructions designed to redirect the agent, reveal data or trigger a dangerous call. Treat all retrieved content as untrusted input unless it has been separately validated.
- Keep authorization logic outside the model’s context and reasoning.
- Never let text in a document or tool description expand the agent’s permissions.
- Do not expose secrets to the model merely so it can pass them to a tool; use a broker that injects only the minimum required credential at execution.
- Limit outbound network destinations and high-impact tools.
- Validate identifiers and parameters at the tool boundary, including tenant, record, path and environment.
- Use separate identities and policies for multi-agent hand-offs; do not treat an upstream agent’s claim as proof of authority.
OWASP identifies prompt injection, tool abuse, exfiltration and excessive autonomy as core agent risks. Its guidance is available in the AI Agent Security Cheat Sheet and AI Agent and MCP Security.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Log, monitor, review and revoke
Permission design is incomplete without a lifecycle. Log the agent identity, initiating user when present, tool, operation, target, result, approval, token or credential use and every permission change. Preserve enough context to reconstruct what happened without placing secret values in logs.
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Monitor for behavior outside the purpose statement: unexpected APIs, unusual token activity, access to new resources, repeated denials, unplanned permission grants and activity in the wrong environment. Alert on changes to the identity, policy or credential rather than waiting for an anomalous business result.
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Review whether the agent is still necessary and whether each permission remains justified. Microsoft’s Entra guidance recommends sign-in and audit-log monitoring, access reviews and sponsor attestation every 6–12 months for its Agent ID deployments. That cadence is Microsoft guidance for Entra, not a universal rule; use a shorter interval for higher-risk agents or after major scope changes. Disable the identity and revoke credentials during an incident, when an owner leaves, or when the agent is decommissioned.
A practical implementation sequence
- Describe the task. Write the purpose, owner, environment, approved data and explicit exclusions.
- Create the principal. Provision a distinct agent identity; separate development, test and production.
- Draft the deny-first manifest. Start with no tools, then list each allowed tool, operation, resource and data boundary.
- Select the authority flow. Use a service flow for autonomous work or a delegated flow for user-context work; follow the target platform’s current documentation.
- Issue constrained credentials. Use the narrowest audience and lifetime available; keep secrets outside model-readable locations.
- Implement the execution check. At every call, validate principal, action, target, scope, expiration and approval state.
- Add approval gates. Require fresh confirmation for sending, deleting, exporting, purchasing, deploying and permission changes.
- Test denials as well as successes. Attempt an excluded repository, a write with a read token, an expired token, a different tenant and an unapproved high-impact action. Each should fail safely and produce an audit event.
- Operate the lifecycle. Monitor, review, right-size, rotate and revoke according to risk and documented ownership.
How to compare two permission designs
When choosing between a convenient broad grant and a task-bounded design, score both against the same questions:
- Does each agent have a distinct identity and accountable sponsor?
- Are resources and data classes limited to the task?
- Are read, write, export, delete and administration distinguishable?
- Are credentials short-lived, isolated and unavailable to model-readable context?
- Is the exact principal, operation and target checked when the call executes?
- Are high-impact actions gated by fresh approval and reversibility controls?
- Can logs show calls, approvals, denials and permission changes?
- Is there a defined review, incident-revocation and decommissioning process?
A setup that is quicker because it grants standing access to an entire tenant or production environment is not equivalent to one that binds authority to a task, target and time window. Convenience at provisioning becomes exposure during prompt injection, configuration error or credential theft.
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What current standards work does—and does not—settle
NIST’s NCCoE published a February 2026 concept paper, Accelerating the Adoption of Software and AI Agent Identity and Authorization. It presents a proposed project and open questions, including how to establish least privilege when an agent’s required actions may be unpredictable, how to bind agent identity to human identity for human-in-the-loop authorization, and how to support auditing and non-repudiation. NIST’s announcement gave April 2, 2026 as the public-comment deadline. The paper is not a final prescriptive standard, so organizations should continue applying enforceable identity, scope, approval and audit controls while implementation guidance evolves.
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