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software-mansion

Argent

Official
by software-mansion
OverviewSchemaRelated ServersScoreDiscussions
TypeScript
Local

screenshot

Capture the current screen of a target iOS simulator, Android emulator, or connected device to inspect UI state or establish a baseline before interaction.

Instructions

Capture a screenshot of the device screen (iOS simulator or physical device, Android emulator, Apple TV simulator, Vega, or Chromium app). Returns { image }; the MCP adapter renders it as a visible image unless the caller passed includeImageInContext: false. Use when you need a baseline image before an interaction or to inspect the current screen state after a delay. Fails if the simulator-server / emulator backend / Chromium CDP is not reachable for the given device.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
udidYesTarget device id from `list-devices` (iOS UDID, Android serial, Apple TV UDID, Vega serial, or Chromium id).
scaleNoScale factor (0.01-1.0). Defaults to ARGENT_SCREENSHOT_SCALE env var, or 0.25 if unset for iOS/Android. On Chromium the default is 1.0 (no downscale); pass <1 to opt in. Downscaling on Chromium requires the optional `sharp` dependency.
rotationNoOrientation override for the screenshot (rotates the captured image after Page.captureScreenshot on Chromium). On Android the capture already follows the device's rotation. Ignored on physical iPhones.
downscalerNoDownscaling algorithm when scale<1 on Chromium. Defaults to lanczos3 (highest quality). Mirrors sim-server's wire enum. Ignored on physical iPhones.
includeImageInContextNoDefault true. Set false only when capturing a full-resolution PNG (scale: 1.0) to save as a baseline/current for screenshot-diff — the file is still written, but the image bytes are not attached to the agent context.

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. Changed2 schema fields changedv0.24.0
    • changedInput schema / properties / downscaler / description
      Previous value: -"Downscaling algorithm when scale<1 on Chromium. Defaults to lanczos3 (highest quality). Mirrors sim-server's wire enum."New value: +"Downscaling algorithm when scale<1 on Chromium. Defaults to lanczos3 (highest quality). Mirrors sim-server's wire enum. Ignored on physical iPhones."
    • changedInput schema / properties / rotation / description
      Previous value: -"Orientation override for the screenshot (rotates the captured image after Page.captureScreenshot on Chromium). On Android the capture already follows the device's rotation."New value: +"Orientation override for the screenshot (rotates the captured image after Page.captureScreenshot on Chromium). On Android the capture already follows the device's rotation. Ignored on physical iPhones."
  2. Changed2 schema fields changedv0.22.0
    • changedInput schema / properties / rotation / description
      Previous value: -"Orientation override for the screenshot (rotates the captured image after Page.captureScreenshot on Chromium)."New value: +"Orientation override for the screenshot (rotates the captured image after Page.captureScreenshot on Chromium). On Android the capture already follows the device's rotation."
    • changedInput schema / properties / scale / description
      Previous value: -"Scale factor (0.01-1.0). Defaults to ARGENT_SCREENSHOT_SCALE env var, or 0.3 if unset for iOS/Android. On Chromium the default is 1.0 (no downscale); pass <1 to opt in. Downscaling on Chromium requires the optional `sharp` dependency."New value: +"Scale factor (0.01-1.0). Defaults to ARGENT_SCREENSHOT_SCALE env var, or 0.25 if unset for iOS/Android. On Chromium the default is 1.0 (no downscale); pass <1 to opt in. Downscaling on Chromium requires the optional `sharp` dependency."
  3. First observedv0.15.0

TDQS

A4.3/5.0
Behavior4/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains the return shape, how the MCP adapter renders the image, the effect of includeImageInContext, and a key failure condition when the backend is unreachable. It does not over-claim or contradict annotations.

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 sentences, each earning its place: the first defines the action and result, the second gives usage guidance, and the third states a practical failure mode. The most important information is front-loaded and there is no redundant filler.

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?

Despite having no output schema and no annotations, the description covers the supported platforms, the return value representation, the adapter rendering behavior, the primary use cases, and the main failure scenario. This is sufficient for an agent to decide when and how to call the tool 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?

The input schema already describes all 5 parameters with 100% coverage, so the baseline is 3. The description adds some context around includeImageInContext by tying it to whether the MCP adapter renders the image, but it does not meaningfully enrich the meaning of the other parameters beyond the schema.

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?

The description names a specific verb and resource: 'Capture a screenshot of the device screen,' and enumerates all supported device types. This clearly distinguishes it from screenshot-diff and other inspection tools by stating exactly what it produces.

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?

The description gives explicit when-to-use guidance: 'Use when you need a baseline image before an interaction or to inspect the current screen state after a delay.' It does not explicitly list when-not-to-use cases or point to alternative tools, but the stated use cases are clear enough for tool selection.

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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