browser_wait_for · Byob MCP: Risk & Policy

WHAT IT DOES

What browser_wait_for does on Byob

AI agents invoke browser_wait_for to trigger actions in Byob. 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 browser_wait_for needs a policy

This tool executes browser control operations by blocking script execution and waiting for DOM state transitions. While not directly destructive or financial, it is a trigger/control mechanism for browser automation that could be chained with other tools (browser_click, browser_eval) to perform arbitrary web interactions.

From the tool's definition Tool performs browser automation actions that wait for and detect DOM state changes. Described as 'Block until a CSS selector reaches the requested state', which is a blocking control flow operation that triggers conditional browser behavior.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_wait_for Rate-limited

browser_wait_for 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": {
    "browser_wait_for": {
      "limits": [
        {
          "counter": "browser_wait_for_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 Byob, so you can run agents against it safely.

FAQ

Questions about browser_wait_for

What does the browser_wait_for tool do? +

Block until a CSS selector reaches the requested state (visible / hidden / attached / detached). It is categorised as a Execute tool in the Byob MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on browser_wait_for? +

Register the Byob MCP server in PolicyLayer and add a rule for browser_wait_for: 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 Byob. Nothing to install.

What risk level is browser_wait_for? +

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

Can I rate-limit browser_wait_for? +

Yes. Add a rate_limit block to the browser_wait_for 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_wait_for completely? +

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

browser_wait_for is provided by the Byob MCP server (wxtsky/byob). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.