Captures the main desktop screen as PNG or JPEG with dimensions, enabling visual inspection of layout, colors, and icons when structural data is insufficient.
视觉通道：截取主屏幕。返回 PNG/JPEG（base64）与尺寸。 用于看布局、颜色、图标等结构通道拿不到的信息。 需要控制消息体积时传 maxWidth（如 1280）+ format:"jpeg"。
| Name | Required | Description | Default |
|---|---|---|---|
| format | No | png 或 jpeg，默认 png | |
| maxWidth | No | 图片最大宽度（像素） | |
| includePng | No | 是否返回图片数据，默认 true；只想拿尺寸可设 false |
Changes observed during successful MCP inspections.
v0.2.2Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden and does solid work: it discloses the return format and that dimensions are included, plus a practical cost/payload tradeoff. It does not state capture scope (full virtual desktop vs. primary monitor) or whether other windows occlude the result, which matters for a screenshot tool.
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?
Three short lines, each doing distinct work: what it captures and returns, why it is different from the structural channel, and how to control size. Front-loaded and zero filler.
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?
No output schema exists, but the description still states the return shape (encoded image + dimensions), so an agent knows what to expect. Residual gap is operational context — multi-monitor/DPI behavior and capture scope — which is not covered anywhere else.
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?
Schema coverage is 100%, so baseline is 3, but the description adds genuine meaning: it explains the joint use of maxWidth and format as a payload-size lever, with a concrete example value. That is behavioral guidance the schema's terse per-field descriptions do not convey.
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?
Opening line states a specific verb and resource: 截取主屏幕 (capture the main screen), and immediately names the return payload (PNG/JPEG base64 + dimensions). The second line differentiates it from the structural/accessibility channel (desktop_elements, desktop_perceive), which is the key sibling distinction an agent needs.
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?
Explicitly says when to reach for this tool: to see layout, colors, and icons that the structural channel cannot provide. It also gives a concrete usage recipe (pass maxWidth ~1280 + format:"jpeg" when message size matters). It does not mention the browser-specific alternative desktop_cdp_screenshot, so it falls short of a full when/when-not map.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.