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polyscreen-mcp

by Shenepoy
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Tap Android display

mobile_input_tap

Inject a display-targeted tap at logical coordinates on an Android device. Pass a UI ref or x/y; ref takes priority to target elements.

Instructions

Inject a display-targeted touchscreen tap in logical display coordinates. Pass ref from the latest UI read, or x and y. ref wins when both are set. Prefer ref over a node's raw center.

Input Schema

NameRequiredDescriptionDefault
xNo
yNo
refNoRef from the latest mobile_ui_snapshot, mobile_ui_find, or mobile_ui_wait on this serial and display. Wins over x and y.
serialYesExact ADB serial from mobile_devices_list; never inferred when multiple devices exist
displayIdYesAndroid framework logical display ID, not a SurfaceFlinger physical ID

Output Schema

NameRequiredDescriptionDefault
dataYes
deviceYes
backendYes
displayNo
warningsYes
durationMsYes
operationIdYes
schemaVersionYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed4 schema fields changedv0.9.0
    • changedInput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
    • addedInput schema / properties / ref
      Added value: +{
+  "description": "Ref from the latest mobile_ui_snapshot, mobile_ui_find, or mobile_ui_wait on this serial and display. Wins over x and y.",
+  "pattern": "^@n\\d+$",
+  "type": "string"
+}
    • changedInput schema / required
      Previous value: -[
-  "serial",
-  "displayId",
-  "x",
-  "y"
-]New value: +[
+  "serial",
+  "displayId"
+]
    • changedOutput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
  2. First observedv0.5.0

TDQS

A4.2/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the agent knows this is a non-destructive, non-idempotent mutation. The description adds the staleness constraint ('latest UI read') and the coordinate-space semantics, but says nothing about error behavior when a ref is stale or a tap targets an off-screen location.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, zero filler, with the action and coordinate space front-loaded and the ref-vs-x/y precedence rule immediately after. Every sentence carries distinct information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need no explanation, and the annotations cover the safety profile. What remains thin is side-effect/failure context for a mutation tool (what a tap does if the ref is stale or the coordinates are outside the display), but the essentials for calling it correctly are present.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 60%, and the description partially compensates: it explains the x/y vs ref precedence and advises preferring ref over a node's raw center, which is guidance the schema does not contain (the schema only says ref 'wins over x and y'). The coordinate-space phrasing also clarifies displayId's meaning.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Inject a display-targeted touchscreen tap') plus the coordinate space ('logical display coordinates'). This is unambiguously the single-tap input tool, distinguishable from mobile_input_double_tap, mobile_input_long_press, and mobile_input_drag without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives clear operational context: the ref must come from 'the latest UI read,' and ref is preferred over x/y or a node's raw center. It does not, however, name when to reach for a sibling input tool (double_tap, long_press) instead, so it stops short of full alternative routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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