Capture and save an Android device screenshot to disk for visual evidence or fallback; the saved path becomes the default baseline for later image comparisons.
截屏存盘（视觉兜底/证据）；路径会记住，作为 vision.diff 缺省基线
| Name | Required | Description | Default |
|---|---|---|---|
| path | No |
Changes observed during successful MCP inspections.
v0.5.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full burden. It does disclose real behavior beyond the schema: it writes a file to disk and the path is remembered as persistent state feeding vision.diff's default baseline. It omits what is returned, overwrite behavior, and whether the path is optional or auto-generated.
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?
A single compact clause with the action front-loaded and the cross-tool consequence appended. No filler, though it is terse enough to feel underspecified rather than optimally structured.
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?
For a simple 1-param tool with no output schema, the description covers the core action and the vision.diff linkage. It still leaves gaps on return value and the optional path default, which matter for calling it correctly.
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 'path' param has 0% schema description coverage. The description adds meaning by explaining that the path is remembered and reused as vision.diff's default baseline, but it doesn't state the format, whether it is optional, or what happens when omitted.
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?
States a specific verb+resource (screenshot saved to disk) and adds a distinguishing role: it becomes the default baseline for vision.diff. This differentiates it from vision.ocr/vlm/ask, though it doesn't explicitly contrast against ui2.screen_evidence or the other capture tools.
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?
'视觉兜底/证据' (visual fallback/evidence) implies when to reach for it – when structured UI queries fail or proof is needed – and it names its downstream relationship to vision.diff. However there is no explicit when-not guidance or named alternative to prefer first, so usage is only implied.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.