extension_tool_userscripts_get_registered

THE RISK

Low Risk

Why extension_tool_userscripts_get_registered needs a policy

This tool queries and retrieves existing userscript registrations based on filter criteria. It reads data about userscripts but does not create, modify, delete, or execute them. The retrieval of metadata about registered scripts poses minimal risk as it is purely informational.

From the tool's definition The tool name includes 'get_' and the description states 'Get specific registered userscripts by filter', which are retrieval operations with no side effects.

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

POLICY

How to control extension_tool_userscripts_get_registered

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

policy.json

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

extension_tool_userscripts_get_registered is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

Related tools and policies

More WebMCP tools

Destructive extension_tool_userscripts_unregister Unregister userscripts by ID or filter Execute call_extension_tool Execute a browser extension tool. Use this to call extension tools that provide browser-le Execute call_website_tool Execute a tool from a website MCP server. Use this to call website-specific tools that you Execute extension_tool_userscripts_test_execute Test execute a script without registering it (Chrome 135+) Execute extension_tool_userscripts_configure_world Configure USER_SCRIPT world properties Execute extension_tool_userscripts_register Register a new userscript with Chrome userScripts API Write extension_tool_userscripts_reset_world Reset USER_SCRIPT world configuration to defaults Write extension_tool_userscripts_update Update existing userscripts

All 13 WebMCP tools →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

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 extension_tool_userscripts_get_registered

What does the extension_tool_userscripts_get_registered tool do? +

Get specific registered userscripts by filter. It is categorised as a Read tool in the WebMCP MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on extension_tool_userscripts_get_registered? +

Register the Web MCP server in PolicyLayer and add a rule for extension_tool_userscripts_get_registered: 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 WebMCP. Nothing to install.

What risk level is extension_tool_userscripts_get_registered? +

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

Can I rate-limit extension_tool_userscripts_get_registered? +

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

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

extension_tool_userscripts_get_registered is provided by the Web MCP server (miguelspizza/webmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every WebMCP tool call.

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

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