Robot Actions — Remote Device Control

Webpage screenshot

webpage_screenshot

Read-onlyIdempotent

Screenshot the web page in the device browser (iOS Safari or Android Chrome, auto-detected). ANDROID: a clean capture of the web CONTENT — pass selector or ref to capture just that element (scrolled into view). iOS: element-clipped web capture is unavailable, so this returns the full DEVICE frame (includes the Safari chrome/status bar); selector/ref clipping is Android-only and is ignored on iOS (a note is returned). Returns a JPEG image.

Input Schema

TableJSON Schema

Name	Required	Description
`ref`	No	Android only: capture just this element, named by a ref from a page-elements listing
`udid`	Yes	Device UDID / serial (iOS or Android)
`pageId`	No	Target page/tab id — auto-picked when omitted
`socket`	No	Android only: abstract unix socket name (default: chrome_devtools_remote)
`selector`	No	Android only: capture just this element (CSS selector), scrolled into view
`platformVersion`	No	Ignored (kept for compatibility)

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedAug 9, 2026

addedInput schema / properties / ref

Added value: +{
+  "description": "Android only: capture just this element, named by a ref from a page-elements listing",
+  "type": "string"
+}

First observedAug 4, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the safety profile is covered. The description adds genuinely useful behavior beyond that: iOS returns the full device frame including Safari chrome/status bar, and selector/ref are ignored on iOS with a note returned, plus the JPEG return type. It does not address failure modes or capture latency, so not a 5.

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

Conciseness4/5

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

The core action is front-loaded and the Android/iOS split is well organized with clear labels. It is slightly dense and capitalizes keywords heavily, but every clause conveys platform-specific behavior rather than filler.

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?

Given no output schema, the description correctly states the return type (JPEG) and explains the platform-dependent capture differences and ignored params. It is complete enough to invoke correctly; minor gaps remain around error cases and how `pageId`/`socket` interact, but those are documented in the schema.

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 100% so the baseline is 3, but the description adds meaning the schema lacks: that `selector`/`ref` clipping is Android-only, scrolled-into-view, and actively ignored on iOS with a returned note. This clarifies the conditional semantics of those params beyond their per-field schema text.

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?

States a specific verb+resource ('Screenshot the web page in the device browser') and clarifies the scope is web content inside iOS Safari/Android Chrome. It implicitly distinguishes itself from device_screenshot by contrasting web-content capture with the full device frame, though it never names sibling tools like web_screenshot or session_screenshot, leaving some routing to inference.

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 conditional context: use `selector`/`ref` on Android for element-clipped capture, and know that on iOS you get the full device frame instead. However, it offers no explicit when-to-use-vs-alternatives routing (e.g., when to prefer this over web_screenshot or device_screenshot), so an agent must infer the boundaries.

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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