query_users_vast

THE RISK

Low Risk

Why query_users_vast needs a policy

This tool retrieves user information from a VAST cluster without creating, modifying, deleting, or executing any operations. It is a read-only query that returns existing data. The severity is low because user name enumeration poses minimal direct risk compared to tools that modify infrastructure or data.

From the tool's definition Tool name includes 'query', description states 'Query user names from VAST cluster', and the endpoint accessed ('users/names') is a straightforward data retrieval operation with no modification or execution capabilities.

Documented attack patterns abuse exactly the kind of access query_users_vast gives an agent:

POLICY

How to control query_users_vast

PolicyLayer is an MCP gateway — it sits between your AI agents and VAST Admin MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for query_users_vast:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "query_users_vast": {}
  }
}

query_users_vast is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register VAST Admin MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

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EXPLORE

Related tools and policies

More VAST Admin MCP Server tools

Execute create_support_bundle_vast Create a support bundle on a VAST cluster for diagnostics and troubleshooting Write create_clone_vast Create a clone from a snapshot Write create_quota_vast Create or update quota for a specific path and tenant Write create_snapshot_vast Create a snapshot for a VAST view Write create_view_from_template_vast Create a new VAST view from a predefined template Write create_view_vast Create a new VAST view Read describe_tool_vast Get tool schema with examples and accepted formats Read list_clusters_vast Retrieve information about configured VAST clusters

All 16 VAST Admin MCP Server tools →

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about query_users_vast

What does the query_users_vast tool do? +

Query user names from VAST cluster using users/names endpoint. It is categorised as a Read tool in the VAST Admin MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on query_users_vast? +

Register the VAST Admin MCP Server MCP server in PolicyLayer and add a rule for query_users_vast: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches VAST Admin MCP Server. Nothing to install.

What risk level is query_users_vast? +

query_users_vast is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit query_users_vast? +

Yes. Add a rate_limit block to the query_users_vast rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block query_users_vast completely? +

Set action: deny in the PolicyLayer policy for query_users_vast. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides query_users_vast? +

query_users_vast is provided by the VAST Admin MCP Server MCP server (vast-data/vast-admin-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every VAST Admin MCP Server tool call.

Start from VAST Admin MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →