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

This is exemplary behavioral disclosure far beyond the minimal annotations (readOnlyHint:false, destructiveHint:false). The description reveals that clicked=true only means the CGEvent was POSTED with no delivery confirmation, that busy/modal/input-ignoring apps report identical success, and that element_disabled is returned only when AXEnabled=false is actually published — a control lacking AXEnabled is treated as unknown and clicked. These caveats directly prevent an agent from drawing false conclusions about side effects.

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?

Four sentences, each earning its place: the core action is front-loaded in sentence one, the return-value caveat in sentence two, the verification advice in sentence three, and the disabled/permission semantics in sentence four. It is dense rather than short, but the length is justified because every clause carries information an agent would otherwise mis-learn at runtime.

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 tool with 5 parameters, one nested object, and no output schema, the description covers the return shape ({clicked, at:{x,y}}), failure semantics, permission requirements, and edge-case behavior — essentially compensating for the missing output schema. Minor gaps remain: it never says where element_ref comes from (e.g., ui_read_tree or ui_find_element), and it doesn't specify the behavior when neither element_ref nor coords is supplied.

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 80%, placing the baseline at 3, but the description adds genuine value beyond the schema: it explains that element_ref is clicked at its center, that coords is the alternate targeting mode, and that element_ref and coords are mutually exclusive alternatives. It compensates for the one undocumented parameter (element_ref has no schema description) by giving it semantic meaning in the first sentence.

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 precise verb+resource: "Clicks an element (by element_ref, at its center) or a screen coordinate (by coords)." The mechanism details (center-click, button left|right, count 2 = double-click) make it unambiguous within the ui_* family and clearly distinct from web_click, ui_menu_bar_click, ui_keystroke, and ui_type. The AXEnabled and Accessibility references anchor it to native UI, preventing confusion with the web interaction 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?

The description gives actionable workflow guidance: "Confirm the effect with ui_wait_for_element or ui_read_tree rather than trusting `clicked`" — this tells the agent what to do after invoking the tool and names the sibling verification tools. It also flags the Accessibility permission prerequisite. It stops short of explicit when-not-to-use exclusions (e.g., 'for menu bar use ui_menu_bar_click, for browser use web_click'), so it earns a 4 rather than a 5.

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