select_database_by_number

THE RISK

Medium Risk

Why select_database_by_number needs a policy

This tool changes the active/selected database context based on a numbered result from a prior browse operation. It modifies state (the current database selection) rather than purely reading data, but does not delete or execute arbitrary code. Severity is low since it only changes a session-level context setting, not data itself.

From the tool's definition Select a database by its number from the browse results

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

POLICY

How to control select_database_by_number

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "select_database_by_number": {
      "limits": [
        {
          "counter": "select_database_by_number_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

select_database_by_number stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

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

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More MCP Data Visualization Server tools

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All 28 MCP Data Visualization Server tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about select_database_by_number

What does the select_database_by_number tool do? +

Select a database by its number from the browse results. It is categorised as a Write tool in the MCP Data Visualization Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on select_database_by_number? +

Register the MCP Data Visualization Server MCP server in PolicyLayer and add a rule for select_database_by_number: 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 MCP Data Visualization Server. Nothing to install.

What risk level is select_database_by_number? +

select_database_by_number is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit select_database_by_number? +

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

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

select_database_by_number is provided by the MCP Data Visualization Server MCP server (xoniks/mcp-visualization-duckdb). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP Data Visualization Server tool call.

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

CHECK YOUR STACK →