screenshotCapture a PNG image of the target's viewport to check visual layout, rendering accuracy, and image display.
Capture a PNG screenshot of the target's viewport. Prefer dom_snapshot for reading content; use this for visual layout, rendering and image checks.
| Name | Required | Description | Default |
|---|---|---|---|
| target_id | Yes | Target id from list_targets — the page / webview / Electron window to inspect. |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish the operation is read-only, idempotent, and non-destructive. The description adds useful behavioral context beyond the annotations: the output is a PNG and the scope is the target's viewport. It does not mention rate limits or return mechanics, but these are not critical given the annotation coverage.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two short sentences communicate the core behavior, output format, and usage guidance without any filler. The most important action is front-loaded, and every sentence earns its place.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With one well-documented parameter, complete annotations, and clear guidance contrasting it with a sibling, the description fully supports correct invocation. No output schema exists, but the PNG screenshot behavior is clearly stated, so an agent knows what to expect.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The single parameter target_id is fully documented in the schema, so the description does not need to add parameter details. The description adds no additional semantic meaning beyond what the schema already provides, making the baseline 3 appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description uses a specific verb and resource: 'Capture a PNG screenshot of the target's viewport.' It also distinguishes the tool from dom_snapshot by stating it is for visual layout, rendering, and image checks rather than content reading.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description explicitly says to prefer dom_snapshot for reading content and to use this tool for visual layout, rendering, and image checks. This directly tells an agent when to choose it over a named sibling tool.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.