list_instances_of_class

THE RISK

Low Risk

Why list_instances_of_class needs a policy

This tool queries and retrieves data from the Italian government data catalog without creating, modifying, deleting, or executing any operations with side effects. It is purely exploratory/informational. The low severity reflects minimal risk even in misuse scenarios, as listing catalog instances cannot harm data or systems.

From the tool's definition Tool description states 'List instances of a given class in the catalog' — a retrieval operation with no modification or deletion. The verb 'list' is a classic read-only query operation.

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

POLICY

How to control list_instances_of_class

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

policy.json

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

list_instances_of_class 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 Schema Gov It 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.

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EXPLORE

Related tools and policies

More Schema Gov It MCP Server tools

Execute query_external_endpoint Execute a SPARQL query against any public HTTPS SPARQL endpoint. Args: - endpointUrl: URL Execute query_local_ontology Execute a SPARQL SELECT query against an ontology available on the server filesystem or th Execute query_sparql Execute a RAW SPARQL query against schema.gov.it. Args: - query: The SPARQL query to exec Execute query_uploaded_store Execute a SPARQL SELECT query against a temporary ontology store created via HTTP upload. Write get_upload_instructions Returns the exact curl command to upload a local RDF file to this MCP server and get back Read explore_dataset Get details of a specific Dataset including metadata and distributions. Use this for targ Read navigate_skos_hierarchy Navigate a SKOS hierarchy upward and/or downward from a concept. Args: - uri: Concept URI Read suggest_improvements Analyze the ontology for structural issues. Args: - limit: Maximum issues per category (d

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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 list_instances_of_class

What does the list_instances_of_class tool do? +

List instances of a given class in the catalog. Args: - class_uri: URI of the class (e.g. It is categorised as a Read tool in the Schema Gov It MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_instances_of_class? +

Register the Schema Gov It MCP Server MCP server in PolicyLayer and add a rule for list_instances_of_class: 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 Schema Gov It MCP Server. Nothing to install.

What risk level is list_instances_of_class? +

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

Can I rate-limit list_instances_of_class? +

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

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

list_instances_of_class is provided by the Schema Gov It MCP Server MCP server (italia/dati-semantic-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Schema Gov It MCP Server tool call.

Start from Schema Gov It 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 →