Teams often assume that preloading every tool schema makes the system simpler, when it actually expands the agent’s surface area and wastes context on unused definitions. Another common mistake is treating a large catalog as automatically usable in every workflow. In practice, teams need relevance-based discovery, tight authorization handling, and clear rules for what the agent may reach for.
What teams underestimate about tool catalogs at scale
The mistake is thinking the catalog is the product. In practice, the catalog is a control surface, and every added integration increases discovery load, policy complexity, and the chance that the agent reaches for a tool that was never meant for that workflow. The real design problem is not “how many tools can we expose?”, but “how do we keep selection relevant, bounded, and reviewable?”
Large catalogs also create a false sense of coverage. Teams often assume that because a tool exists, it will be used appropriately, but agents do not infer intent the way humans do. If the catalog lacks clear routing rules, capability scoping, and authorization boundaries, the agent may select a technically available tool that is operationally wrong or too powerful for the task.
That is why MCP catalog design needs to be treated as a governance and authorization problem, not just an integration inventory. A smaller, better-curated set of tools usually produces better outcomes than a broad catalog that makes everything appear equally reachable. MCP Security Guide is useful here because it frames MCP authorization, token handling, and tool risk as first-class design concerns rather than afterthoughts.
Why hundreds of integrations make the wrong tools more likely
At catalog scale, the failure mode is not only overload, it is ambiguity. If multiple tools can satisfy a similar request, the agent needs a strong basis for choosing one that is safe, contextually correct, and allowed under the current workflow. Without that, teams end up with broad permissions, ad hoc prompting, or brittle filters that look precise but fail in edge cases.
Another common error is treating all integrations as equally trustworthy. A catalog may include internal services, third-party connectors, and one-off utilities with very different blast radii. Once those are flattened into a single menu, the agent can no longer distinguish high-value routines from risky shortcuts unless the platform enforces that distinction elsewhere.
This is where authorization and provenance matter more than raw count. Relevance-based discovery should decide what is even eligible to appear, while policy should decide what the agent is permitted to invoke. NHIMG’s AI Agent Identity Security: The 2026 Deployment Guide is a good companion for this issue because it connects agent lifecycle, least privilege, and task-scoped access to practical deployment decisions.
For broader context on why capability overexposure becomes an attack surface, OWASP Agentic AI Top 10 is relevant because tool misuse and identity and privilege abuse are exactly the kinds of failures that large catalogs can amplify.
What good catalog design looks like in practice
Good MCP catalog design starts with filtering, not just listing. Teams should expose tools by workflow, environment, and trust level, then require explicit authorization logic for anything that can reach sensitive systems or execute side effects. If the agent can invoke the tool, the question is not merely whether the tool exists, but whether the request context is sufficient to justify use.
Catalog hygiene also needs operational discipline. Tool descriptions should be specific enough to support selection, but not so verbose that they waste context on definitions the agent will never use. Equally important, unused or stale integrations should be removed quickly, because dormant entries still expand the decision space and can become accidental escalation paths later.
Where catalogs include external or high-risk connectors, teams should add approval gates, scoped credentials, and clear fallbacks for uncertain matches. Model Context Protocol: Authorization specification is the right external reference for the underlying authorization model, especially where audience-bound tokens and token passthrough constraints affect tool access decisions.
When the catalog is large enough that operators can no longer explain why a tool was chosen, the design has gone too far. A useful rule is that every integration should have an owner, a clear risk tier, and a defined reason for inclusion; if any one of those is missing, the tool is probably present for convenience rather than necessity.
Risk and Threat Considerations
Large tool catalogs increase exposure by widening the set of reachable actions, credentials, and downstream systems. That makes it easier for a mistaken selection, malicious prompt, or poisoned tool response to turn a routine request into unauthorized access or unintended execution.
Failure mechanism: The agent is offered too many eligible tools, weakly differentiated permissions, or overbroad credentials, then selects a tool that is allowed by the interface but unsafe in the workflow. In the worst cases, attacker-controlled content can steer selection toward a tool that leaks data, executes commands, or crosses environment boundaries.
Impact: The blast radius expands from a single workflow mistake to broader data exposure, privilege misuse, credential reuse, or action on the wrong system. In large catalogs, the real security problem is often not a single vulnerable integration, but the cumulative effect of many integrations with uneven trust and weak selection controls.
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 API Security 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 |
|---|---|---|
| OWASP Agentic AI Top 10 | ASI02 — Tool Misuse | Large MCP catalogs raise the chance of unsafe tool selection. |
| ASI03 — Identity & Privilege Abuse | Catalog scale can amplify overbroad access and privilege misuse. | |
| Recommendation — Limit eligible tools and validate tool choice against workflow intent. Scope agent privileges tightly before exposing additional tools. | ||
| OWASP API Security Top 10 | API9 — Improper Inventory Management | Hundreds of integrations need disciplined inventory and lifecycle control. |
| Recommendation — Maintain a current tool inventory and retire stale integrations promptly. | ||
| NIST SP 800-53 Rev 5 | AC-6 — Least Privilege | Tool reach should be constrained to the minimum needed for the workflow. |
| IA-5 — Authenticator Management | Catalogs often rely on credentials and tokens that need lifecycle control. | |
| Recommendation — Enforce least privilege on every tool and connector the agent can invoke. Rotate and scope credentials used by tools and connectors. | ||
Practitioner Guidance
What to prioritise: Start by classifying integrations into a small number of risk tiers, then expose only the subset that is genuinely eligible for the current workflow. The decision point should be whether the agent needs the capability, not whether the capability exists somewhere in the platform.
What to verify: Confirm that each tool has a business owner, an explicit authorization boundary, and a clear trigger for when it may be selected. If operators cannot explain why a tool is in the catalog or what blocks its use, it is not curated enough.
Common mistake: Teams often try to solve scale with bigger catalogs and better prompts. That usually fails because prompt quality cannot compensate for weak tool eligibility rules, stale entries, or broad access paths.
Practitioner takeaway: The safest MCP catalogs are not the largest ones, they are the ones where discovery is constrained, authorization is explicit, and every reachable tool has a defensible reason to be there.
Related resources from NHI Mgmt Group
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
