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Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already carry the safety profile, and the description adds genuinely useful behavioral detail: the return is an image, burst returns 'one image in rows of four', and pictures are costlier than the accessible tree. It does not, however, explain the surprising readOnlyHint=false (e.g. that park moves the pointer) or any side effects, so it adds moderate context rather than rich disclosure.

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?

Front-loaded and free of filler, but the compressed, fragmentary phrasing hurts clarity ('vision checks nothing is told apart by color alone' is grammatically broken and ambiguous). It is dense rather than wasteful, but some sentences do not parse cleanly on first read.

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 7-parameter tool with no output schema, the description covers purpose, selection, cost, and most parameter intent adequately. Remaining gaps (park semantics, the readOnlyHint=false rationale) are minor and partly covered by the schema.

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 the baseline is 3, but the description goes beyond the schema strings by explaining the intent behind window-vs-screen, cropping, vision modes, and burst layout. Only 'park' and 'session' are left entirely to the schema.

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 ('A picture of the screen, or of one window, RETURNED AS AN IMAGE') and immediately differentiates it from the sibling accessible_tree by naming the alternative. An agent can tell this is the visual-capture tool without opening the schema.

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?

Gives explicit when-to-use ('the only way to see colors, layout and what's drawn'), names the competing option (accessible_tree) and the cost tradeoff, then prescribes preferences ('take the window rather than the screen, and crop when you need a part') plus scenario routing (vision for color-alone checks, burst for motion/animation/transition). This is close to a complete selection guide.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.