rpc_tap · Rpcclient MCP: Risk & Policy

WHAT IT DOES

What rpc_tap does on Rpcclient

AI agents invoke rpc_tap to trigger actions in Rpcclient. 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 rpc_tap needs a policy

This tool executes a tap gesture on a live iOS device at caller-specified coordinates. The effect is entirely argument-dependent — tapping could dismiss dialogs, submit forms, trigger purchases, or perform any other UI action.

From the tool's definition "Tap by normalized screen coordinates" — triggers a physical tap action on an iOS device, performing an external operation (UI interaction) whose effects depend on the coordinates provided

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

rpc_tap Rate-limited

rpc_tap 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": {
    "rpc_tap": {
      "limits": [
        {
          "counter": "rpc_tap_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 Rpcclient, so you can run agents against it safely.

FAQ

Questions about rpc_tap

What does the rpc_tap tool do? +

Tap by normalized screen coordinates, useful for focusing non-AX web fields. It is categorised as a Execute tool in the Rpcclient MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on rpc_tap? +

Register the Rpcclient MCP server in PolicyLayer and add a rule for rpc_tap: 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 Rpcclient. Nothing to install.

What risk level is rpc_tap? +

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

Can I rate-limit rpc_tap? +

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

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

rpc_tap is provided by the Rpcclient MCP server (appknox/rpcclient-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.