browser_keyboard_up · MCProxy MCP: Risk & Policy

WHAT IT DOES

What browser_keyboard_up does on MCProxy

AI agents invoke browser_keyboard_up to trigger actions in MCProxy. 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_keyboard_up needs a policy

Releasing a held key is a browser interaction/execution action. It can trigger form submissions, keyboard shortcuts, or other browser-level events depending on context. While seemingly minor in isolation, within a headless browser automation framework it constitutes executing an external operation. Severity is medium because misuse could trigger unintended actions in web applications being automated.

From the tool's definition 'Release a held key' — this triggers a keyboard input event in a headless browser, representing an external browser action whose effects depend on arguments (which key is released and the current browser context).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_keyboard_up Rate-limited

browser_keyboard_up 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_keyboard_up": {
      "limits": [
        {
          "counter": "browser_keyboard_up_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 MCProxy, so you can run agents against it safely.

FAQ

Questions about browser_keyboard_up

What does the browser_keyboard_up tool do? +

Release a held key. It is categorised as a Execute tool in the MCProxy 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_keyboard_up? +

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

What risk level is browser_keyboard_up? +

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

Can I rate-limit browser_keyboard_up? +

Yes. Add a rate_limit block to the browser_keyboard_up 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_keyboard_up completely? +

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

browser_keyboard_up is provided by the MCProxy MCP server (saladtechnologies/mcproxy). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.