fill_element · Visual Annotation MCP: Risk & Policy

WHAT IT DOES

What fill_element does on Visual Annotation MCP

AI agents use fill_element to create or update resources in Visual Annotation MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Visual Annotation MCP environment.

WHY IT NEEDS A POLICY

Why fill_element needs a policy

This tool writes text into form input elements, which constitutes reversible modification of data. While it does not delete or execute arbitrary code, it can alter form state and potentially submit sensitive information or trigger downstream automation.

From the tool's definition Tool name 'fill_element' and description 'Fill an inspected input-like element id with text' indicates the tool modifies input field values, creating or updating data in a web form.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

fill_element Rate-limited

fill_element stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "fill_element": {
      "limits": [
        {
          "counter": "fill_element_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about fill_element

What does the fill_element tool do? +

Fill an inspected input-like element id with text. It is categorised as a Write tool in the Visual Annotation MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on fill_element? +

Register the Visual Annotation MCP server in PolicyLayer and add a rule for fill_element: 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 Visual Annotation MCP. Nothing to install.

What risk level is fill_element? +

fill_element is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit fill_element? +

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

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

fill_element is provided by the Visual Annotation MCP server (mstocker1/visual_annotation_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.