Delegated access preserves a link to the original user consent and can be constrained to a specific tool, audience, and task. Shared credentials detach access from that context, so the same secret can be reused far beyond the intended workflow. In MCP, delegated access is governable; shared credentials are only controllable if tightly wrapped in policy.
How delegated access differs from shared credentials in MCP workflows
delegated access keeps the permission tied to a specific consented user, tool, audience, and task, which makes the access path governable and auditable. Shared credentials collapse that context into one reusable secret, so the same bearer material can be copied, reused, and exercised outside the original workflow. In MCP environments, that difference determines whether access remains bounded or becomes broadly transferable.
Delegation is a control model, not just a convenience pattern. It lets the server or broker evaluate who approved the action, what resource is in scope, and whether the request still matches the original intent. Shared credentials do the opposite: they turn the credential itself into the authority, so whoever possesses it can often act as if they were the original approved subject.
MCP makes this distinction more visible because tool access is often narrow, session-like, and task-specific. Delegated access aligns well with that design because it can be limited to a tool, audience, or transaction, while shared credentials tend to outlive the workflow that created them. A credential that is valid across multiple tools or environments may still work technically, but it no longer expresses the original permission boundary.
Why context and blast radius are not the same thing
With delegated access, the security question is whether the token or grant still represents the right actor and the right purpose. With shared credentials, the security question shifts to whether the secret has been protected well enough that reuse will not occur in another place, by another process, or after the workflow has changed. That is why delegated access can usually be reviewed in terms of consent, scope, and expiry, while shared credentials must be treated as high-blast-radius material.
Delegated access also supports revocation in a meaningful way. If the original user withdraws consent, the access path can be invalidated without rotating every downstream system that happened to copy the secret. Shared credentials are harder to unwind because they are detached from the originating context; once leaked or redistributed, they often need full secret rotation and a search for every place they were embedded.
MCP authorization guidance is built around this idea of audience-bound, non-passthrough tokens, which is why it is a better fit for delegated access than for reusable shared secrets. The same design principle is reinforced by RFC 8693, where token exchange preserves delegation while changing the token used for a particular resource or downstream hop.
What this means for MCP architects and operators
In practice, delegated access is the safer default when an MCP server is acting on behalf of a user, because it preserves provenance and allows policy to follow the request. Shared credentials are only acceptable when the surrounding controls effectively compensate for the loss of context, for example by tightly constraining where the secret can be used, how long it lives, and which workflow can present it. Without those wrappers, a shared credential is functionally a portable secret, not a governed delegation.
Human vs Non-Human Identity helps frame why this matters operationally: delegated access preserves the user relationship, while shared credentials often blur ownership and accountability across people and systems. That same governance problem shows up in API key management and secrets management, where rotation, scoping, and revocation are the controls that make reusable secrets less dangerous.
OWASP Non-Human Identity Top 10 and RFC 6749 are useful reference points when you need to separate governed delegated access from bearer-material reuse. Where the system cannot preserve audience, expiry, and task scope, you should treat the pattern as credential sharing rather than delegation.
Risk and Threat Considerations
Shared credentials in MCP environments create a larger abuse surface because any party that sees the secret may inherit the same access, regardless of whether they were part of the original workflow. The main risk is not only theft, but silent reuse: a secret that is copied into logs, scripts, integrations, or prompts can continue to work long after the intended task has ended.
Failure mechanism: the access path loses its original context, so the system can no longer distinguish approved delegation from copied bearer use. That enables overuse, lateral reuse across tools or environments, and delayed detection when the secret is exercised outside the intended audience.
Impact: the blast radius expands from one sanctioned action to any action that the shared secret can authorize, which can expose data, trigger unintended tool calls, or create persistent access that survives user intent and normal approval review.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP API Security Top 10 and OWASP Non-Human Identity Top 10 address 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 |
|---|---|---|
| NIST SP 800-53 Rev 5 | IA-9 — Service Identification and Authentication | MCP delegation and shared-secret use both hinge on service-to-service authentication. |
| AC-2 — Account Management | Delegated access and shared credential handling both depend on lifecycle control and revocation. | |
| IA-5 — Authenticator Management | Shared credentials are authenticator material that must be issued, rotated, and revoked carefully. | |
| Recommendation — Use IA-9 to replace reusable secrets with authenticated, scoped service interactions. Use AC-2 to manage approval, deprovisioning, and revocation of access paths. Use IA-5 to govern secret issuance, rotation, and recovery for shared credentials. | ||
| OWASP API Security Top 10 | API2 — Broken Authentication | Shared credentials and weak delegation boundaries both create authentication abuse risk in API-mediated MCP flows. |
| Recommendation — Harden authentication so access tokens cannot be reused beyond their intended context. | ||
| OWASP Non-Human Identity Top 10 | NHI-02 — Secret Leakage | Shared credentials become dangerous when copied, exposed, or reused outside the intended workflow. |
| Recommendation — Eliminate secret leakage paths and rotate any credential that may have been copied. | ||
Practitioner Guidance
What to prioritize: prefer delegated access for any MCP flow where a user, tool, or task can be identified, then require shared credentials to be the exception rather than the default. If a workflow can be expressed as consent plus audience plus expiry, it should usually be implemented that way.
What to verify: confirm that the token or grant is audience-bound, short-lived, and revocable without rotating unrelated systems. If you cannot point to the exact resource, task, and expiry that govern the access, you are probably looking at credential reuse rather than true delegation.
Common mistake: treating a shared secret as acceptable because it is stored in a vault or passed through a proxy. Storage and transit protections help, but they do not restore the context that delegation provides.
Practitioner takeaway: In MCP, the key question is whether authority follows consent or follows possession, because only the former keeps access bounded to the original intent.
Related resources from NHI Mgmt Group
- What is the difference between role-based access and shared credentials in clinical environments?
- What is the difference between stored credentials and OAuth-based MCP access?
- What is the difference between delegated AI access and shared agent identities?
- What is the difference between OAuth Token Exchange and AuthZEN in delegated MCP access?