puppeteer_fill · Server Puppeteer MCP: Risk & Policy

WHAT IT DOES

What puppeteer_fill does on Server Puppeteer

AI agents invoke puppeteer_fill to trigger actions in Server Puppeteer. 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 puppeteer_fill needs a policy

This tool performs a browser automation action (filling an input field), which constitutes an external operation with side effects depending on the arguments (e.g., submitting credentials, entering search queries, populating forms). It falls under Execute as it drives real browser interactions whose consequences depend on what field is targeted and what value is entered.

From the tool's definition 'Fill out an input field' — triggers a browser action that interacts with a live web page input field via Puppeteer automation

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

puppeteer_fill Rate-limited

puppeteer_fill 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": {
    "puppeteer_fill": {
      "limits": [
        {
          "counter": "puppeteer_fill_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 Server Puppeteer, so you can run agents against it safely.

FAQ

Questions about puppeteer_fill

What does the puppeteer_fill tool do? +

Fill out an input field. It is categorised as a Execute tool in the Server Puppeteer MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on puppeteer_fill? +

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

What risk level is puppeteer_fill? +

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

Can I rate-limit puppeteer_fill? +

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

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

puppeteer_fill is provided by the Server Puppeteer MCP server (@hisma/server-puppeteer). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.