lookup_columns

THE RISK

Low Risk

Why lookup_columns needs a policy

lookup_columns performs read-only operations against ServiceNow's metadata (sys_dictionary table). It retrieves schema information about table columns without creating, modifying, executing, deleting, or financial operations. The blast radius is minimal as it only exposes structural metadata already accessible to authenticated ServiceNow users.

From the tool's definition Tool description states it 'List or search columns (fields)' and 'Queries the sys_dictionary' — both are query operations with no modification or execution capability.

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

POLICY

How to control lookup_columns

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

policy.json

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

lookup_columns 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 Now Sdk Ext — 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

Related tools and policies

More Now Sdk Ext tools

Destructive cancel_flow Cancel a running or paused flow execution by its context ID. Destructive query_delete_records Find records matching an encoded query and delete them all. Execute aggregate_grouped Run aggregate functions (COUNT, AVG, MIN, MAX, SUM) grouped by a field on any Execute execute_action Execute a ServiceNow Flow Designer action by scoped name. Execute execute_flow Execute a published ServiceNow Flow Designer flow by scoped name. Execute execute_script Execute JavaScript on a ServiceNow instance using Scripts - Background Execute execute_subflow Execute a ServiceNow Flow Designer subflow by scoped name. Execute run_atf_test Execute a single ServiceNow ATF (Automated Test Framework) test by its sys_id.

All 86 Now Sdk Ext tools →

Read 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.
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 lookup_columns

What does the lookup_columns tool do? +

List or search columns (fields) on a ServiceNow table. Queries the sys_dictionary. It is categorised as a Read tool in the Now Sdk Ext MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on lookup_columns? +

Register the Now Sdk Ext MCP server in PolicyLayer and add a rule for lookup_columns: 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 Now Sdk Ext. Nothing to install.

What risk level is lookup_columns? +

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

Can I rate-limit lookup_columns? +

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

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

lookup_columns is provided by the Now Sdk Ext MCP server (sonisoft-cnanda/now-sdk-ext-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Now Sdk Ext tool call.

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

CHECK YOUR STACK →