create_client_script · ServiceNow- MCP: Risk & Policy

WHAT IT DOES

What create_client_script does on ServiceNow-MCP

AI agents invoke create_client_script to trigger actions in ServiceNow-MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why create_client_script needs a policy

This tool creates executable JavaScript that runs in the ServiceNow client context on form events. While it 'creates' an artifact (Write), its primary risk is that the script executes in users' browsers on ServiceNow form interactions. Malicious or misconfigured client scripts can exfiltrate data, manipulate form behavior, or perform unauthorized actions at scale across all users who load affected forms.

From the tool's definition 'Create a new client script (onLoad, onChange, onSubmit, onCellEdit)' and 'requires SCRIPTING_ENABLED=true'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_client_script Rate-limited

create_client_script stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "create_client_script": {
      "limits": [
        {
          "counter": "create_client_script_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches ServiceNow-MCP, so you can run agents against it safely.

FAQ

Questions about create_client_script

What does the create_client_script tool do? +

Create a new client script (onLoad, onChange, onSubmit, onCellEdit) (requires SCRIPTING_ENABLED=true). It is categorised as a Execute tool in the ServiceNow-MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on create_client_script? +

Register the ServiceNow- MCP server in PolicyLayer and add a rule for create_client_script: 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 ServiceNow-MCP. Nothing to install.

What risk level is create_client_script? +

create_client_script is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit create_client_script? +

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

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

create_client_script is provided by the ServiceNow- MCP server (tedorigawa001/servicenow-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.