User identity proves who initiated the work, while agent identity proves which software entity is actually performing the call. In MCP-based workflows, both matter because an action can be initiated by a person but executed by an autonomous agent on their behalf. Strong systems bind authorization to both identities so the right actor is allowed to do the right action.
How agent identity differs from user identity in an MCP workflow
User identity answers the question, “Who asked for this?” Agent identity answers, “Which software entity is actually executing the tool call?” In MCP-based workflows, that split matters because the person and the agent may share intent, but they do not share authority by default. The security boundary is stronger when systems preserve both the human initiator and the acting agent as separate, attributable subjects.
The practical difference is not semantic, it is operational. A user can approve a task, but an agent may still need its own registration, authentication material, scoped permissions, and lifecycle controls. That is why MCP authorization guidance treats the server as the resource boundary and expects tokens, audiences, and delegated access to be evaluated in relation to the acting component, not just the requesting person.
For teams designing these flows, the key question is whether the workflow can prove both initiation and execution. If the answer is no, you may know who started the action, but not which agent performed it, which makes auditing, revocation, and blast-radius analysis much harder. The distinction becomes more important as agents operate across multiple tools, sessions, and environments on behalf of a single user.
Why both identities must be bound to authorization
In a well-designed MCP flow, the user’s identity establishes intent and policy context, while the agent’s identity establishes execution authority. Those are different trust decisions. If authorization is tied only to the user, an over-permissive agent can act beyond what the workflow intended. If it is tied only to the agent, the system may lose the human accountability needed for approval, review, and incident response.
This is where delegation becomes central. The safest pattern is to grant the agent only the minimum authority needed for the specific task, and to preserve the user context as an input to policy decisions rather than as a substitute for agent authentication. The most useful model is “user approves, agent acts, system records both.” That keeps the chain of custody intelligible when something goes wrong.
Good MCP practice is to treat the agent as a distinct security principal even when it is acting on behalf of a user. MCP authorization guidance is explicit about audience-bound tokens and avoiding token passthrough, which helps prevent a user token from becoming a generic credential that every tool can reuse.
The same logic is why delegated token exchange patterns matter. When an agent needs to act for a person, the system should be able to show what was delegated, to whom, and for how long, instead of collapsing both actors into one opaque session.
What this means for auditing, failures, and policy design
Once you separate user identity from agent identity, the audit trail becomes more useful. You can answer who initiated the request, which agent executed it, what scope it had, and whether the action stayed within the intended delegation. That is especially important in MCP workflows because tool access can be broad, stateful, and hard to unwind after the fact.
The common failure mode is identity flattening: the platform logs only the user, only the agent, or a blended session that cannot distinguish the two. That makes approval workflows look stronger than they are, because the human may have approved a task without explicitly approving the exact agent capabilities used to complete it. It also makes containment harder when an agent is compromised or misconfigured.
For identity and access design, the useful comparison is to treat user identity as the source of intent and agent identity as the subject of operational privilege. The agent should have its own lifecycle, rotation, offboarding, and revocation path. If an agent can no longer be trusted, removing the user’s access is not enough if the agent still holds valid credentials or delegated tokens.
Risk and Threat Considerations
The main risk is authority confusion, where an attacker, misconfiguration, or overly broad integration causes user intent to be mistaken for agent authority, or agent authority to outlive the user action that created it. In MCP-based workflows that can expose secrets, expand tool access, or let a compromised agent act with permissions that were never meant to be reusable.
Failure mechanism: A delegated workflow collapses user and agent identity into one trust decision, so the agent inherits more authority than the task requires, or retains valid access after the user context has ended.
Impact: This can produce unauthorized tool execution, weak attribution, delayed revocation, and a larger blast radius if the agent, token, or tool channel is abused.
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 addresses the attack and risk surface, while NIST SP 800-53 Rev 5 sets the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Agentic AI Top 10 | ASI03 — Identity & Privilege Abuse | MCP workflows hinge on agent authority and delegated execution. |
| ASI02 — Tool Misuse | MCP agents can overuse or misuse tool access once authorized. | |
| Recommendation — Bind tool authorization to the acting agent and the approving user. Scope agent tool access to the minimum required action. | ||
| NIST SP 800-53 Rev 5 | IA-9 — Identification and Authentication (Service, API, and Application) | Agent identity in MCP maps to service-style authentication and trust. |
| AC-6 — Least Privilege | Delegated agent permissions should be narrower than user intent. | |
| AU-2 — Event Logging | Separate user and agent identities improve attribution in MCP workflows. | |
| Recommendation — Authenticate the agent as a distinct non-human principal. Limit each agent to the smallest usable permission set. Log initiator, acting agent, delegated scope, and tool use. | ||
Practitioner Guidance
What to verify: Confirm that the workflow can independently log the initiator, the acting agent, the delegated scope, and the exact tool or resource accessed. If you cannot reconstruct those four elements after an incident, the identity model is too coarse for production use.
Decision rule: If the agent can make network, file, data, or administrative calls without a distinct agent credential or delegated token, treat that as a design flaw, not a convenience. The human may be the approver, but the software entity still needs its own bounded authority.
Common mistake: Teams often rely on the user’s SSO session as if it were enough for everything downstream. In MCP workflows, that shortcut usually creates ambiguous accountability and makes least-privilege enforcement impossible at the agent layer.
Practitioner takeaway: The right model is not “human identity versus agent identity,” it is “human intent plus agent execution,” with both kept visible, bounded, and separately revocable.
Related resources from NHI Mgmt Group
- What is the difference between human identity governance and AI agent governance?
- What is the difference between user-based permissions and least privilege in MCP workflows?
- What is the difference between user identity and agent identity in enterprise AI workflows?
- What is the difference between workload identity and API keys for AI agents?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 30, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
