A registry helps agents discover tools and connection metadata. A gateway decides whether the agent is allowed to use those tools and under what constraints. Enterprises need both, because discovery without enforcement leaves access uncontrolled, while enforcement without discovery forces rigid hardcoded integrations.
Why This Matters for Security Teams
An MCP registry and an mcp gateway solve different security problems, but teams often collapse them into one “MCP platform” and miss the control boundary. A registry is about discoverability: what tools exist, what metadata they publish, and how agents can find them. A gateway is about enforcement: whether a given agent can invoke a tool, with what scope, and under what runtime constraints.
That distinction matters because MCP tool access is already outpacing governance. NHIMG research in The State of MCP Server Security 2025 found that only 18% of mcp server deployments implement any form of access scoping for tool permissions. In practice, that means many environments have discovery without decisioning, which turns the registry into a catalogue of reachable risk rather than a control point. Guidance from the OWASP Agentic AI Top 10 reinforces that agent tool access must be constrained at runtime, not assumed safe because a tool is “known.” In practice, many security teams encounter excessive tool reach only after an agent has already chained access across systems rather than through intentional design.
How It Works in Practice
A registry and a gateway usually sit in sequence. The registry publishes tool names, schemas, endpoints, ownership metadata, and sometimes trust signals such as environment, version, or tenant. The gateway sits in the request path and evaluates whether the agent may call a specific tool for a specific purpose at that moment. In mature designs, the gateway enforces policy using identity, context, and task intent instead of relying on static allowlists alone.
For security teams, the practical split is simple: the registry improves selection, while the gateway provides control. The registry helps an agent discover the least ambiguous tool for a job, but it should not be trusted to decide access. The gateway should validate the calling workload identity, inspect the request, and apply policy-as-code rules for scope, data sensitivity, location, tenant, and time window. This is why current guidance from both OWASP Top 10 for Agentic Applications 2026 and NHIMG’s Ultimate Guide to NHIs treats identity and authorization as separate layers.
- Use the registry for tool metadata, ownership, and version awareness.
- Use the gateway for authentication, authorization, logging, rate limits, and data guardrails.
- Prefer runtime decisions over static pre-approval lists where agent behaviour is dynamic.
- Bind tool invocation to workload identity so the gateway knows which agent is acting.
This distinction becomes especially important when an agent can infer new tool combinations, since a registry may advertise safe-seeming tools that become risky only when composed together. These controls tend to break down when the registry becomes the de facto policy source and teams assume published metadata is the same thing as enforcement.
Common Variations and Edge Cases
Tighter gateway enforcement often increases integration overhead, requiring organisations to balance developer speed against real access control. That tradeoff is most visible in fast-moving agentic environments, where teams want low-friction tool discovery but still need assurance that the agent is not over-privileged. Best practice is evolving, and there is no universal standard for how much policy should live in the registry versus the gateway.
Some environments use a lightweight registry plus a separate API gateway, while others fold gateway logic into the MCP server itself. That can work, but only if policy evaluation happens at request time and not as a one-time registration check. The risk is higher for autonomous agents, because a tool that looks benign during registration may become sensitive once chained with other actions. NHIMG’s Analysis of Claude Code Security highlights why context-aware controls matter when code-moving or tool-using agents can act faster than manual review can keep up. In environments with many ephemeral agents, a registry without a gateway becomes an index of reachable services rather than a security boundary.
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 CSA MAESTRO address the attack and risk surface, while NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Agentic AI Top 10 | T10 | Agent tool access must be constrained at runtime, not assumed safe from discovery. |
| CSA MAESTRO | M1 | Maps to agent identity, policy enforcement, and control-plane separation for tool use. |
| NIST AI RMF | Supports governing autonomous behaviour with runtime accountability and risk controls. |
Define runtime risk criteria for agent tool use and document who approves and monitors exceptions.
Related resources from NHI Mgmt Group
- What is the difference between managed identities and hardcoded secrets for AI agents?
- What is the difference between human identity governance and AI agent governance?
- What is the difference between workload identity and API keys for AI agents?
- What is the difference between governing human access and governing AI agent access?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on June 23, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
