Start a new automation session. Returns a sessionId needed by all other tools. Automatically attaches to the frontmost app.
AI agents invoke session_start to trigger actions in ScreenHand. 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.
session_start initiates an automation session that grants control over the active application using native accessibility APIs. While the tool itself is a setup/initialization step, it enables all downstream Execute capabilities (browser control, UI interaction, applescript execution, app launching).
From the tool's definition Tool 'Start a new automation session' with 'Automatically attaches to the frontmost app' indicates initiation of system-level control.
Documented attack patterns abuse exactly the kind of access session_start gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and ScreenHand, and nothing reaches the server without passing your rules. This is the rule we recommend for session_start:
{
"version": "1",
"default": "deny",
"tools": {
"session_start": {
"limits": [
{
"counter": "session_start_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}session_start 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.
Free to start. No card required.
Start a new automation session. Returns a sessionId needed by all other tools. Automatically attaches to the frontmost app. It is categorised as a Execute tool in the ScreenHand MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the ScreenHand MCP server in PolicyLayer and add a rule for session_start: 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 ScreenHand. Nothing to install.
session_start 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 session_start 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 session_start. 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.
session_start is provided by the ScreenHand MCP server (manushi4/screenhand). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from ScreenHand, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
89 ScreenHand tools catalogued and risk-classified — across an index of 43,000+ MCP servers.