AI agents invoke screen_on to trigger actions in uiautomator2 MCP Server. 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.
Based on the server context (Android device automation) and the tool name, this likely turns the device screen on — a device state change that triggers an external operation. This is an Execute-level action since it changes device state. Confidence is reduced due to empty description.
From the tool's definition Tool name 'screen_on' on a server that controls Android devices via uiautomator2; description is empty.
Documented attack patterns abuse exactly the kind of access screen_on gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and uiautomator2 MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for screen_on:
{
"version": "1",
"default": "deny",
"tools": {
"screen_on": {
"limits": [
{
"counter": "screen_on_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}screen_on 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.
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screen_on. It is categorised as a Execute tool in the uiautomator2 MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the uiautomator2 MCP Server MCP server in PolicyLayer and add a rule for screen_on: 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 uiautomator2 MCP Server. Nothing to install.
screen_on is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the screen_on 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.
Set action: deny in the PolicyLayer policy for screen_on. 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.
screen_on is provided by the uiautomator2 MCP Server MCP server (tanbro/uiautomator2-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from uiautomator2 MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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77 uiautomator2 MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.