Set the value of a UI element (text field, slider, etc.). Searches by title first, falls back to value match.
AI agents use ui_set_value to create or update resources in ScreenHand — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your ScreenHand environment.
This tool modifies the state of UI elements by setting their values. It creates or changes data in UI controls, which is a reversible write operation. However, misuse could lead to unintended form submissions or configuration changes depending on what element is targeted.
From the tool's definition Set the value of a UI element (text field, slider, etc.)
Documented attack patterns abuse exactly the kind of access ui_set_value 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 ui_set_value:
{
"version": "1",
"default": "deny",
"tools": {
"ui_set_value": {
"limits": [
{
"counter": "ui_set_value_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}ui_set_value stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Set the value of a UI element (text field, slider, etc.). Searches by title first, falls back to value match. It is categorised as a Write tool in the ScreenHand MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the ScreenHand MCP server in PolicyLayer and add a rule for ui_set_value: 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.
ui_set_value is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the ui_set_value 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 ui_set_value. 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.
ui_set_value 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.
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89 ScreenHand tools catalogued and risk-classified — across an index of 43,000+ MCP servers.