tap · Espresso MCP: Risk & Policy

WHAT IT DOES

What tap does on Espresso

AI agents invoke tap to trigger actions in Espresso. 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 tap needs a policy

This tool triggers an external operation (a UI interaction) on a connected Android device. The tap action could trigger arbitrary in-app behavior depending on the coordinates — submitting forms, navigating, confirming dialogs, etc. Effects depend on arguments and the current app state, making it Execute category. Misuse could lead to unintended actions on the device, hence medium severity.

From the tool's definition Simulate a tap on the connected Android device at the specified coordinates

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

tap Rate-limited

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": {
    "tap": {
      "limits": [
        {
          "counter": "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 Espresso, so you can run agents against it safely.

FAQ

Questions about tap

What does the tap tool do? +

Simulate a tap on the connected Android device at the specified coordinates. It is categorised as a Execute tool in the Espresso MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on tap? +

Register the Espresso MCP server in PolicyLayer and add a rule for 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 Espresso. Nothing to install.

What risk level is tap? +

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

Can I rate-limit tap? +

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

Set action: deny in the PolicyLayer policy for 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 tap? +

tap is provided by the Espresso MCP server (vs4vijay/espresso-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.