Capture a specified app window's visible area as a PNG returned via MCP image, using exact instance and target IDs. Confirm privacy scope before sharing.
获取指定应用窗口的可见区域 PNG，以 MCP image 返回，不落盘。可能包含用户隐私，请先确认分享范围。
| Name | Required | Description | Default |
|---|---|---|---|
| targetId | Yes | 由 desirecore_list_windows 返回的确切 targetId；不默认挑窗口。 | |
| instanceId | Yes | 由 desirecore_list_instances 返回的本次运行 instanceId；实例重启后必须重新列举并选择，不接受端口或路径。 |
Changes observed during successful MCP inspections.
v1.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering safety and side-effect profile. The description adds two valuable behavioral details beyond annotations: the result is returned as an MCP image and is not saved to disk ('不落盘'), and it warns about potential user privacy, advising confirmation of sharing scope. These add meaningful context without contradicting the annotations.
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, efficient sentence that front-loads the core purpose, followed by a privacy note. Every word earns its place; there is no redundancy or filler, making it easy for an agent to parse quickly.
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 2-parameter tool with fully described schema and no output schema, the description is quite complete: it states the return type (MCP image), the side-effect (no disk persistence), and a privacy caveat. It could mention error conditions or prerequisites, but those are implicitly handled by the schema's requirement that instanceId and targetId come from listing tools. The completeness is strong for the tool's complexity.
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% — both parameters (instanceId and targetId) are fully described in the input schema, including their origin (from list_instances and list_windows). The tool description itself adds no additional parameter semantics, so the baseline of 3 is appropriate when the schema carries the explanatory burden.
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 clearly states the tool's function: capturing the visible area of a specified application window as a PNG, returned as an MCP image. It uses a specific verb ('获取' / get) and a specific resource (visible area of an app window), and the sibling tools (list, status, cdp) make this the only screenshot tool, so it is easily distinguished.
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 implies the use case (taking a screenshot of a window) but does not explicitly state when to use it versus alternatives, nor does it mention any exclusions or conditions. It is clear from context that this is the screenshot tool, but explicit guidance like 'use this when you need the window's visual content' is absent.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.