browser_fill_form

THE RISK

Low Risk

Why browser_fill_form needs a policy

The tool name suggests filling out a browser form, which could be a Write or Execute action, but the description is completely empty, making it impossible to determine the exact behavior. Given the server context (AWS Managed Prometheus MCP server) and the sibling tools present, this tool seems out of place. Without a description, confidence is very low.

From the tool's definition Tool name is 'browser_fill_form' but description is empty or uninformative; name suggests browser form filling action

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

POLICY

How to control browser_fill_form

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "browser_fill_form": {
      "limits": [
        {
          "counter": "browser_fill_form_rate",
          "window": "minute",
          "max": 60,
          "scope": "grant"
        }
      ]
    }
  }
}

browser_fill_form gets a rate cap, and everything else on the server is denied unless you say otherwise.

Create a free account and register Prometheus 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.

SET A RULE FOR THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Tool risk categories → How PolicyLayer classifies MCP tools by what they can do.
MCP tool → What an MCP tool is and how clients discover and call it.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about browser_fill_form

What does the browser_fill_form tool do? +

browser_fill_form. It is categorised as a Other tool in the Prometheus MCP Server MCP Server, which means it performs auxiliary operations.

How do I enforce a policy on browser_fill_form? +

Register the Prometheus MCP Server MCP server in PolicyLayer and add a rule for browser_fill_form: 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 Prometheus MCP Server. Nothing to install.

What risk level is browser_fill_form? +

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

Can I rate-limit browser_fill_form? +

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

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

browser_fill_form is provided by the Prometheus MCP Server MCP server (awslabs.prometheus-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Prometheus MCP Server tool call.

Start from Prometheus 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 →