webview_screenshotCapture a WebView page screenshot on a specified mobile device and save it to a local path, returning the file path for later access.
page 级截图(Page.captureScreenshot)并落盘,返回文件路径(不回传 base64)。
| Name | Required | Description | Default |
|---|---|---|---|
| device | Yes | 目标设备 serial(同 mobile_list_available_devices 的 id) | |
| saveTo | Yes | 保存绝对路径,如 D:\\tmp\\wv.png |
Changes observed during successful MCP inspections.
v0.0.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description transparently discloses that the tool captures a screenshot and writes it to disk, but the annotations declare readOnlyHint=true. Writing a file is a side effect that modifies the environment, so the description contradicts the annotation. Per the rubric, this contradiction forces a score of 1.
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?
The description is a single dense sentence with no filler. It packs the protocol, output behavior, and a negative constraint (no base64) into minimal wording.
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 no output schema, the description explicitly covers the return value (file path) and format exclusion (not base64). Both required parameters are fully documented. Minor gaps include prerequisites such as an established webview connection, but these are reasonably inferable from sibling webview tools.
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 description coverage is 100%: device is cross-referenced to mobile_list_available_devices, and saveTo is documented with an absolute-path example. The description adds no parameter-specific meaning beyond the schema, so baseline 3 is 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 states a specific action ('page 级截图' using Page.captureScreenshot), the output behavior (save to disk and return file path), and an explicit exclusion (no base64). This distinguishes it from mobile screenshot tools like mobile_take_screenshot and mobile_save_screenshot.
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 'page 级' phrasing implies this is for webview page screenshots rather than device-level screenshots, and the sibling tools include webview_connect and mobile_take_screenshot. However, it does not explicitly state when to use this tool versus mobile_save_screenshot/mobile_take_screenshot or mention prerequisites like a connected webview.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.