set_text · Linux Computer Use MCP: Risk & Policy

WHAT IT DOES

What set_text does on Linux Computer Use

AI agents invoke set_text to trigger actions in Linux Computer Use. 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 set_text needs a policy

This tool modifies the content of UI text fields by replacing their values using AT-SPI accessibility APIs or keyboard simulation. It triggers external UI operations that can have wide-ranging effects depending on what text field is targeted — from filling form fields to modifying configuration inputs. Since it directly manipulates the state of running applications through UI automation, it falls under Execute.

From the tool's definition Replace value of an @eN text/entry via AT-SPI (falls back to ctrl+a + type)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_text Rate-limited

set_text 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": {
    "set_text": {
      "limits": [
        {
          "counter": "set_text_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 Linux Computer Use, so you can run agents against it safely.

FAQ

Questions about set_text

What does the set_text tool do? +

Replace value of an @eN text/entry via AT-SPI (falls back to ctrl+a + type). It is categorised as a Execute tool in the Linux Computer Use MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on set_text? +

Register the Linux Computer Use MCP server in PolicyLayer and add a rule for set_text: 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 Linux Computer Use. Nothing to install.

What risk level is set_text? +

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

Can I rate-limit set_text? +

Yes. Add a rate_limit block to the set_text 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 set_text completely? +

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

set_text is provided by the Linux Computer Use MCP server (tak-uukti/linux-computer-use). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.