polyscreen-mcp

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Type Android text

mobile_input_text

Type text through ADB's virtual keyboard on Android devices. Pass a ref to tap a node first; reports Unicode limitations instead of hiding them.

Instructions

Type text through ADB's virtual keyboard. Pass ref to tap that node first. Reports the Unicode limitation instead of hiding it.

Input Schema

Name	Required	Description
`ref`	No	Ref from the latest mobile_ui_snapshot, mobile_ui_find, or mobile_ui_wait on this serial and display.
`text`	Yes
`serial`	Yes	Exact ADB serial from mobile_devices_list; never inferred when multiple devices exist
`displayId`	Yes	Android framework logical display ID, not a SurfaceFlinger physical ID

Output Schema

Name	Required	Description	Default
`data`	Yes
`device`	Yes
`backend`	Yes
`display`	No
`warnings`	Yes
`durationMs`	Yes
`operationId`	Yes
`schemaVersion`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedv0.9.0Oct 13, 2026

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.",
+  "pattern": "^@n\\d+$",
+  "type": "string"
+}

changedOutput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

First observedv0.5.0Jul 25, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already declare readOnly=false, idempotent=false, destructive=false, openWorld=false, so the safety profile is covered. The description adds genuinely new behavioral context: that a ref causes a prior tap on that node, and that Unicode input is a known limitation that will be surfaced rather than silently swallowed. It does not say what happens to existing field content.

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 with no filler, and the primary action is front-loaded before the ref precondition and the caveat. Every sentence carries distinct information.

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

Completeness5/5

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

With an output schema present and annotations covering the safety/mutation profile, the description does not need to explain return values. It covers the action, the ref precondition, and the Unicode caveat, which is what an agent needs to call this correctly.

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

Parameters3/5

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

Schema description coverage is 75%, so the baseline is 3. The description does add real meaning for ref (it triggers a tap before typing, not just a lookup key), which the schema only implies. It adds nothing for text length limits or displayId.

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

Purpose4/5

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

Specific verb+resource: 'Type text through ADB's virtual keyboard', which is clearly distinguishable from the key-event siblings (mobile_input_key, mobile_input_key_sequence). It also discloses the Unicode constraint up front. It stops short of naming an alternative sibling when text entry won't work.

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

Usage Guidelines3/5

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

'Pass ref to tap that node first' gives conditional usage guidance for one parameter, and 'Reports the Unicode limitation instead of hiding it' signals an expected failure mode. However, it never says when to prefer this over mobile_clipboard, mobile_input_key, or other input tools, so usage is implied rather than stated.

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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