The context delivery boundary is the point where tools, prompts, and policy-relevant metadata are handed to an agent. In MCP, that boundary matters because context can influence behaviour before execution, so controls must apply before the first downstream action occurs.
What the Context Delivery Boundary Does
The context delivery boundary is the handoff point where an agent receives prompts, tool definitions, policy-relevant metadata, and other execution-shaping context. Its importance is that the agent can be influenced before it performs any downstream action, so the boundary itself becomes part of the security control surface.
Why the Boundary Matters in MCP
In MCP, the boundary helps separate what is merely available from what is actually delivered into the agent’s working context. That distinction matters because context can change the agent’s next decision, including which tool it selects, how it interprets instructions, and what it treats as authoritative.
Good boundary design reduces ambiguity about where context is introduced, what is allowed to cross, and which fields should be filtered, normalized, or withheld before the first action. This is especially important when context includes policy hints, routing data, tenant-specific information, or other metadata that could alter behaviour without being obvious in the final output.
The Model Context Protocol authorization specification is relevant here because it shows that MCP treats authorization as a transport-level concern, not an afterthought. The context delivery boundary sits close to that decision point, where the system must decide what an agent is permitted to receive.
What Can Go Wrong at the Boundary
A weak boundary can leak more context than the agent needs, preserve stale or contradictory instructions, or allow policy-relevant metadata to cross into runtime unchecked. Once delivered, that context may bias tool use, expand the agent’s apparent authority, or create confusion between user intent, system policy, and operational metadata.
Boundary failure is often subtle because the harmful effect may appear later, after the agent has already accepted the context as part of its decision state. That makes the delivery step a security control point rather than a simple plumbing detail.
The issue also intersects with OWASP Non-Human Identity Top 10 because context often carries identity-bearing material such as tokens, secrets, or access hints that should not be broadly exposed. If the wrong material reaches the agent, downstream misuse becomes much easier.
OWASP Agentic AI Top 10 also maps well to this concept, especially where delivered context can enable tool misuse, privilege abuse, or agent hijacking through misleading or overbroad inputs.
How Practitioners Should Think About It
The practical question is not just what context the agent can use, but what context it should receive at all. That means the boundary should be treated as a governed interface, with clear rules for classification, minimisation, and authorization of context before delivery.
Practitioners should also distinguish persistent configuration from transient request context. Mixing those layers makes it harder to tell whether the agent is acting on current instructions or inherited state, which increases the chance of unsafe carryover between sessions, tenants, or tasks.
For infrastructure and control design, the boundary should be reviewed alongside NIST AI Risk Management Framework practices and NIST Cybersecurity Framework 2.0 governance objectives, because both emphasize controlled behavior, risk reduction, and accountable system operation.
MCP authorization guidance is useful here as a reminder that the moment of delivery is part of the authorization story, not separate from it. If a context element changes the agent’s authority or decision space, it belongs under deliberate control.
Risk and Threat Considerations
The main risk is that sensitive, stale, or overly broad context reaches the agent before any protective check can stop it. That can create unintended tool access, policy bypass, prompt manipulation, or trust abuse through information that was never meant to shape execution.
Failure mechanism: An attacker, misconfiguration, or weak integration causes the delivery boundary to pass along harmful instructions, excessive metadata, or sensitive context that changes agent behavior before the first action.
Impact: The agent may act with the wrong assumptions, reveal protected information, invoke tools inappropriately, or become easier to steer toward unsafe or unauthorized outcomes.
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 and OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST AI RMF, NIST CSF 2.0 and NIST SP 800-53 Rev 5 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST AI RMF | Govern | Covers AI governance and risk control over agent behavior shaped by delivered context. |
| Recommendation — Define governance for context delivery so only approved inputs can shape agent behavior. | ||
| NIST CSF 2.0 | GV.OC-01 — Organizational Context | Applies because context delivery depends on governing what information is allowed into operation. |
| Recommendation — Define the operational context and boundaries for what agents may receive and use. | ||
| OWASP Agentic AI Top 10 | ASI03 — Identity & Privilege Abuse | Delivered context can alter an agent's effective authority and access decisions. |
| Recommendation — Constrain delivered context so it cannot expand agent privilege or authority. | ||
| OWASP Non-Human Identity Top 10 | NHI-02 — Secret Leakage | The boundary can expose sensitive tokens or other secret material to an agent. |
| Recommendation — Prevent secrets from crossing the boundary unless they are strictly required. | ||
| NIST SP 800-53 Rev 5 | AC-6 — Least Privilege | Limiting delivered context supports least-privilege execution and reduces overexposure. |
| Recommendation — Restrict delivered context to the minimum needed for the authorized task. | ||
Practitioner Guidance
What to watch for: Treat the boundary as a control point, not a transport detail. Review what crosses it, who can influence it, and whether the agent receives only the minimum context needed for the task.
Governance implication: Ownership should cover both the content delivered and the decision to deliver it, especially when policy metadata, secrets, routing hints, or tenant-specific context are involved.
Practitioner takeaway: If a field can change agent behavior, it needs a deliberate approval path before it crosses the delivery boundary.