preview_dataset

THE RISK

Low Risk

Why preview_dataset needs a policy

preview_dataset retrieves and displays sample data from a dataset for inspection purposes. This is a query/read operation with no side effects, no data modification, and no irreversible actions. The severity is low because viewing dataset previews poses minimal risk — the data accessed is typically already visible to authorized users, and no external operations are triggered.

From the tool's definition Tool description states 'Preview the first N rows of a dataset to inspect its data before downloading' — a read-only inspection operation with no modification, deletion, or execution.

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

POLICY

How to control preview_dataset

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

policy.json

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

preview_dataset 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 MobusMCP — 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 →

Free to start. No card required.

EXPLORE

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All 13 MobusMCP 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 preview_dataset

What does the preview_dataset tool do? +

Preview the first N rows of a dataset to inspect its data before downloading. It is categorised as a Read tool in the MobusMCP MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on preview_dataset? +

Register the Mobus MCP server in PolicyLayer and add a rule for preview_dataset: 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 MobusMCP. Nothing to install.

What risk level is preview_dataset? +

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

Can I rate-limit preview_dataset? +

Yes. Add a rate_limit block to the preview_dataset 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 preview_dataset completely? +

Set action: deny in the PolicyLayer policy for preview_dataset. 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 preview_dataset? +

preview_dataset is provided by the Mobus MCP server (mobus-ai/mobus). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MobusMCP tool call.

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

CHECK YOUR STACK →