sdk_set_value · UI Bridge MCP: Risk & Policy

WHAT IT DOES

What sdk_set_value does on UI Bridge MCP

AI agents use sdk_set_value to create or update resources in UI Bridge MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your UI Bridge MCP environment.

WHY IT NEEDS A POLICY

Why sdk_set_value needs a policy

This tool creates or modifies application state by setting input element values. While it does not delete or execute arbitrary code, it does alter data in external applications, which could have unintended consequences if misused by an agent. It is reversible (a new value can be set), placing it in the Write category rather than Execute or Destructive.

From the tool's definition Tool description states "Set the value of an input element directly in the SDK app." The verb 'set' combined with 'value' indicates modification of data or application state. The tool operates on external applications via SDK mode.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

sdk_set_value Rate-limited

sdk_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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "sdk_set_value": {
      "limits": [
        {
          "counter": "sdk_set_value_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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 sdk_set_value

What does the sdk_set_value tool do? +

Set the value of an input element directly in the SDK app. It is categorised as a Write tool in the UI Bridge MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on sdk_set_value? +

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

What risk level is sdk_set_value? +

sdk_set_value is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit sdk_set_value? +

Yes. Add a rate_limit block to the sdk_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.

How do I block sdk_set_value completely? +

Set action: deny in the PolicyLayer policy for sdk_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.

What MCP server provides sdk_set_value? +

sdk_set_value 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.