capture_singlefile · Chrome Devtools MCP: Risk & Policy

WHAT IT DOES

What capture_singlefile does on Chrome Devtools

AI agents invoke capture_singlefile to trigger actions in Chrome Devtools. 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 capture_singlefile needs a policy

While the tool extracts/reads page content, it actively executes a capture operation through browser automation via Chrome DevTools. This goes beyond passive Read (which would be simple page inspection) into Execute territory—it runs an external process (SingleFile) to generate artifacts based on dynamic arguments.

From the tool's definition Tool description specifies 'Capture the selected page URL as a self-contained SingleFile HTML artifact using the active Chrome DevTools browser session.' This involves triggering an external operation (SingleFile capture) and browser automation whose effects…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

capture_singlefile Rate-limited

capture_singlefile 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": {
    "capture_singlefile": {
      "limits": [
        {
          "counter": "capture_singlefile_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 Chrome Devtools, so you can run agents against it safely.

FAQ

Questions about capture_singlefile

What does the capture_singlefile tool do? +

Capture the selected page URL as a self-contained SingleFile HTML artifact using the active Chrome DevTools browser session. It is categorised as a Execute tool in the Chrome Devtools MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on capture_singlefile? +

Register the Chrome Devtools MCP server in PolicyLayer and add a rule for capture_singlefile: 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 Chrome Devtools. Nothing to install.

What risk level is capture_singlefile? +

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

Can I rate-limit capture_singlefile? +

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

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

capture_singlefile is provided by the Chrome Devtools MCP server (shivamprasad99/chrome-devtools-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.