app_ui_snapshot

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

With no annotations at all, the description carries the full burden and does it well: 'Reads only. Takes no focus, moves no pointer, changes nothing, so it is safe while somebody is working' discloses side-effect profile, focus/pointer behavior and concurrency safety in one stroke. It further clarifies the read boundary (bar vs. contents) so the agent knows exactly what state is and isn't captured.

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 with the one-line summary, then a capitalized rationale and a safety note, so the important content is reached immediately. The 'four calls' anecdote is slightly long for the point it makes, but it justifies the tool's existence rather than padding.

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?

Zero parameters, an output schema present (so return shape needn't be described), and the description still covers scope, inclusion/exclusion of menu contents, and safety. Nothing an agent needs in order to decide to call it and interpret the result is missing.

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 tool takes zero parameters and the schema confirms an empty properties object, so there is nothing for the description to disambiguate. Baseline 4 applies; no parameter-level gap exists.

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 in the first line: a full on-screen inventory of menus, panels, dialogs and toolbars in one call, and frames itself as the UI analogue of app_context. An agent can distinguish it from app_screenshot or app_read_window because the scope ('everything on screen') and the intent ('what am I looking at') are explicit.

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 a clear when-to-use rationale: orientation at the start, replacing the four guessed calls that previously led callers to conclude a capability was missing. It also explains the inclusion boundary (menu bar listed, menu contents not) which implicitly routes content-opening tasks to the click/menu tools, but it never names an explicit alternative such as app_screenshot or app_list_panels.

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