ui_change_buffer_drain · UI Bridge MCP: Risk & Policy

WHAT IT DOES

What ui_change_buffer_drain does on UI Bridge MCP

AI agents invoke ui_change_buffer_drain to trigger actions in UI Bridge MCP. 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 ui_change_buffer_drain needs a policy

Draining a change buffer is an operational/execution action that flushes pending UI changes or queued operations in the runner. It's not a simple read, nor does it clearly destroy data or move money. It executes an internal mechanism, potentially causing side effects depending on what's in the buffer.

From the tool's definition 'Drain the change buffer in the runner' — triggers an internal operational action (draining/flushing a buffer) in the runner process

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ui_change_buffer_drain Rate-limited

ui_change_buffer_drain 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": {
    "ui_change_buffer_drain": {
      "limits": [
        {
          "counter": "ui_change_buffer_drain_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 UI Bridge MCP, so you can run agents against it safely.

FAQ

Questions about ui_change_buffer_drain

What does the ui_change_buffer_drain tool do? +

Drain the change buffer in the runner. It is categorised as a Execute tool in the UI Bridge MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on ui_change_buffer_drain? +

Register the UI Bridge MCP server in PolicyLayer and add a rule for ui_change_buffer_drain: 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 UI Bridge MCP. Nothing to install.

What risk level is ui_change_buffer_drain? +

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

Can I rate-limit ui_change_buffer_drain? +

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

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

ui_change_buffer_drain is provided by the UI Bridge MCP server (qontinui/ui-bridge-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.