Capture the main macOS screen as a PNG in base64, optionally crop to a specified region, and return scale and logical size for accurate point-based click coordinates.
Capture the Mac screen as PNG base64, optionally cropped to region {x,y,w,h}. Returns {scale, logical_size, screen:'main'} for the main display; click coordinates are in points (pixels / scale).
| Name | Required | Description | Default |
|---|---|---|---|
| region | No |
Changes observed during successful MCP inspections.
v0.1.2Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does meaningful work: it discloses the return shape ({scale, logical_size, screen:'main'}), scopes output to the main display, and explains the pixel-to-point conversion needed for subsequent clicks. It omits that this is a read-only operation and any macOS screen-recording permission requirement, which is the main remaining gap.
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 dense sentences, front-loaded with the core action, then crop behavior, then output shape and coordinate units. No filler, and every clause carries information an agent needs.
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, so the description must explain returns — and it does, at least for scale, logical_size and screen. It doesn't say which field carries the base64 image payload or whether multiple displays are supported beyond 'main display', leaving minor ambiguity for a nested-object tool.
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 'region' parameter is a nested object with 0% schema description coverage and no properties defined in the schema, so the description's '{x,y,w,h}' breakdown is essential and well-targeted. However it doesn't clarify optionality semantics (partial region? defaults? validation), so it compensates only partially for the coverage gap.
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 and resource ('Capture the Mac screen as PNG base64') plus an optional crop, and the platform qualifier 'Mac' separates it from sibling screenshots like browser_screenshot and phone_screenshot. It stops short of explicitly naming those siblings, but the domain is unmistakable.
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?
Usage is implied rather than stated: the note that 'click coordinates are in points (pixels / scale)' hints that this tool pairs with mac_click/mac_drag, but no explicit when-to-use or when-to-prefer-an-alternative guidance is given. An agent must infer the screenshot-then-click workflow.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.